angular-cn/public/docs/ts/latest/guide/template-syntax.jade

include ../../../../_includes/_util-fns

:marked
  # Template Syntax
  Our Angular application manages what the user sees and does through the interaction of a Component class instance and its user-facing template.

  Many of us are familiar with the Component/Template duality from our experience with Model-View-Controller or Model-View-ViewModel. In Angular,  the Component plays the part of the Controller/ViewModel and the Template represents the view.

  Let’s find out what it takes to write a Template for our view.

  We’ll cover these basic elements of Template Syntax

  >[HTML](#html)

  >[Interpolation](#interpolation)

  >[Template expressions](#template-expressions)

  >[Template statements](#template-statements)
  
  >[Binding syntax](#binding-syntax)

  >[Property Binding](#property-binding)

  >[Attribute, Class and Style Bindings](#other-bindings)

  >[Event Binding](#event-binding)

  >[Two-way data binding with `NgModel`](#ngModel)

  >[Built-in Directives](#directives)

  >[* and &lt;template>](#star-template)

  >[Local template variables](#local-vars)

  >[Input and Output Properties](#inputs-outputs)

  >[Template Expression Operators](#expression-operators)

  [Live Example](/resources/live-examples/template-syntax/ts/plnkr.html).

.l-main-section
:marked
  ## HTML
  HTML is the language of the Angular template. Our “[QuickStart](./quickstart.html)” application had a template that was pure HTML

+makeExample('template-syntax/ts/app/app.component.html', 'my-first-app')(format=".")
:marked
  Almost all HTML syntax is valid template syntax. The `<script>` element is a notable exception;  it is forbidden in order to eliminate any possibility of JavaScript injection attacks (in practice it is simply ignored).

  Some legal HTML doesn’t make much sense in a template. The `<html>`, `<body>` and `<base>` elements have no useful role in our repertoire. Pretty much everything else is fair game.

  We can extend the HTML vocabulary of our templates with Components and Directives that appear as new elements and attributes. And we are about to learn how to get and set DOM values dynamically through data binding.

  Let’s turn to the first form of data binding - interpolation - to see how much richer Template HTML can be.

.l-main-section
:marked
  ## Interpolation
  We met the double-curly braces of interpolation, `{{` and `}}`, early in our Angular education.
+makeExample('template-syntax/ts/app/app.component.html', 'first-interpolation')(format=".")
:marked
  We use interpolation to weave calculated strings into the text between HTML element tags and within attribute assignments.

+makeExample('template-syntax/ts/app/app.component.html', 'title+image')(format=".")
:marked
  The material between the braces is often the name of a component property. Angular replaces that name with the
  string value of the corresponding component property. In this example, Angular evaluates the `title` and `heroImageUrl` properties
  and "fills in the blanks", displaying first a bold application title and then a heroic image.

  More generally, the material between the braces is a **template expression** that Angular first **evaluates**
  and then **converts to a string**. The following interpolation illustrates the point by adding the two numbers within braces:
+makeExample('template-syntax/ts/app/app.component.html', 'sum-1')(format=".")
:marked
  The expression can invoke methods of the host component as we do here with `getVal()`:
+makeExample('template-syntax/ts/app/app.component.html', 'sum-2')(format=".")
:marked
  Angular evaluates all expressions in double curly braces, converts the expression results to strings, and concatenates them with neighboring literal strings. Finally,
  it assigns this composite interpolated result to an **element or directive property**.

  We appear to be inserting the result between element tags and assigning to attributes.
  It's convenient to think so and we rarely suffer for this mistake.
  But it is not literally true. Interpolation is actually a special syntax that Angular converts into a
  [Property Binding](#property-binding) as we explain below. The implications and consequences can be profound.

  But before we explore that assertion, we’ll take a closer look at template expressions and statements.

<a id="template-expressions"></a>
.l-main-section
:marked
  ## Template Expressions
  A template **expression** produces a value. 
  Angular executes the expression and assigns it to property of a binding target such
  as an HTML element, a component, or a directive.
  
  We put a template expression within the interpolation braces when we wrote `{{1 + 1}}`.
  We’ll see template expressions again in [Property Bindings](#property-binding) , 
  appearing in quotes to the right of the (=) symbol as in `[property]="expression"`.

  We write template expressions in a language that looks like JavaScript. 
  Many JavaScript expressions are legal template expressions but not all.
  JavaScript expressions that have or promote side-effects are prohibited including:
  * assignment (`=`)
  * the `new` operator
  * chaining expressions with `;` or `,`
  * increment and decrement operators, `++` and `--`.

  Other notable differences from JavaScript syntax include:
  * no support for the bit-wise operators, `|` and `&`
  * new [template expression operators](#expression-operators), such as `|` and `?.`
  
  <a id="expression-context"></a>
  ### Expression Context
  
  Perhaps more surprising, we cannot refer to anything in the global namespace.
  We can’t refer to `window` or `document`. We can’t call `console.log` or `Math.max`.
  We are restricted to referencing members of the expression context.
  
  The *expression context* is typically the **component instance**, the source of binding values.

  When we see *title* wrapped in double-curly braces, <code>{{title}}</code>,
  we know that `title` is a property of the data-bound component.
  When we see *isUnchanged* in `[disabled]="isUnchanged"`,
  we know we are referring to that component's `isUnchanged` property.

  The component itself is usually the expression *context* in which case
  the template expression usually references that component.
  
  The expression context may include an object other than the component.
  A [local template variable](#local-vars) is one such alternative context object.
  

  <a id="no-side-effects"></a>
  ### Expression Guidelines
  Template expressions can make or break an application. 
  Please follow these guidelines unless you have an exceptionally good reason to break them
  in specific circumstances that you thoroughly understand.
  
  #### No visible side-effects

  A template expression should have ***no visible side-effects***. 
  We're not allowed to change any application state other than the value of the
  target property.
  
  This rule is essential to Angular's "unidirectional data flow" policy.
  We should never worry that reading a component value might change some other displayed value.
  The view should be stable throughout a single rendering pass.
  
  #### Finish fast
  Angular executes template expressions more often than we might think.
  Expressions should finish quickly or the user experience may drag, especially on slower devices.
  
  #### Keep them simple
  Although we can write quite complex template expressions, we strongly discourage that practice. 
  Most readers frown on JavaScript in the HTML. 
  A property name or method call should be the norm. 
  An occasional Boolean negation (`!`) is OK. 
  Otherwise, confine application and business logic to the component itself where it will be easier to develop and test.    
  
  #### Idempotent Expressions
  An [idempotent](https://en.wikipedia.org/wiki/Idempotence) expression is ideal because
  it is free of side-effects and improves Angular's change detection performance.

  In Angular terms, an idempotent expression always returns *exactly the same thing* until
  one of its dependent values changes.
  
  Dependent values should not change during a single turn of the JavaScript virtual machine.
  If an idempotent expression returns a string or a number, it returns the same string or number
  when called twice in a row. If the expression returns an object (including a `Date` or `Array`),
  it returns the same object *reference* when called twice in a row. 

<a id="template-statements"></a>
.l-main-section
:marked
  ## Template Statements
  
  A template **statement** responds to an ***event*** raised by a binding target 
  such as an element, component, or directive.
  
  We’ll see template statements in [Event Bindings](#event-binding), 
  appearing in quotes to the right of the (=) symbol as in `(event)="statement"`.

  A template statement *has a side-effect*. 
  It's how we update application state from user input.
  There would be no point to responding to an event otherwise.
.l-sub-section
  :marked
    Responding to events is the other side of Angular's "unidirectional data flow".
    We're free to change anything, anywhere, during this turn of the JavaScript virtual machine.
:marked
  Angular template statements are also written in a language that looks like JavaScript.
  The template statement parser is different than the template expression parser and 
  specifically supports both assignment (=) and chaining expressions with semicolons (;) and commas (,).
  
  However, certain JavaScript syntax is not allowed:
  * the `new` operator
  * increment and decrement operators, `++` and `--`
  * bit-wise operators, `|` and `&`
  * the [template expression operators](#expression-operators)
  
  As with expressions, we cannot refer to anything in the global namespace.
  We can’t refer to `window` or `document`. We can’t call `console.log` or `Math.max`.
  
  We are restricted to referencing members of the statement context.
  The **statement context** is typically the **component instance** to which we are binding an event.

  The *onSave* in `(click)="onSave()"` is sure to be a method of the data-bound component instance.
  
  The statement context may include an object other than the component.
  A [local template variable](#local-vars) is one such alternative context object. 
  We'll frequently see the reserved `$event` symbol in event binding statements,
  representing the "message" or "payload" of the raised event. 
.l-sub-section
  :marked
    Although we can write quite complex template statements, we strongly discourage that practice. 
    Most readers frown on JavaScript in the HTML. 
    A method call or simple property assignment should be the norm.
:marked
  Now that we have a feel for template expressions and statements, 
  we’re ready to learn about the varieties of data binding syntax beyond Interpolation.

.l-main-section
:marked
  <a id="binding-syntax"></a>
  ## Binding syntax overview
  Data binding is a mechanism for coordinating what users see with application data values.  
  While we could push values to and pull values from HTML,
  the application is easier to write, read, and maintain if we turn these chores over to a binding framework.
  We simply declare bindings between binding sources and target HTML elements and let the framework do the work.

  Angular provides many kinds of data binding and we’ll discuss each of them in this chapter.
  First we'll take a high level view of Angular data binding and its syntax.

  We can group all bindings into three categories by the direction in which data flows. 
  Each category has its distinctive syntax:
table
  tr
    th Data Direction
    th Syntax
    th Binding Type
  tr
    td One way<br>from data source<br>to view target
    td
      code-example(format="" ).
        {{expression}}
        [target] = "expression"
        bind-target = "expression"
    td.
      Interpolation<br>
      Property<br>
      Attribute<br>
      Class<br>
      Style
    tr
      td One way<br>from view target<br>to data source
      td
        code-example(format="" ).
          (target) = "statement"
          on-target = "statement"
      td Event
    tr
      td Two way
      td
        code-example(format="" ).
          [(target)] = "expression"
          bindon-target = "expression"
      td Two-way
:marked
  Binding types other than interpolation have a **target name** to the left of the equal sign, 
  either surrounded by punctuation (`[]`, `()`) or preceded by a prefix (`bind-`, `on-`, `bindon-`).

  What is that target? Before we can answer that question, we must challenge ourselves to look at Template HTML in a new way.

  ### A New Mental Model

  With all the power of data binding and our ability to extend the HTML vocabulary
  with custom markup, it is tempting to think of Template HTML as “HTML Plus”.
  
  *Well it is HTML Plus*.
  But it’s also significantly different than the HTML we’re used to.
  We really need a new mental model.

  In the normal course of HTML development, we create a visual structure with HTML elements and
  we modify those elements by setting element attributes with string constants.
+makeExample('template-syntax/ts/app/app.component.html', 'img+button')(format=".")
:marked
  We still create a structure and initialize attribute values this way in Angular templates.

  Then we learn to create new elements with Components that encapsulate HTML
  and drop them into our templates as if they were native HTML elements
+makeExample('template-syntax/ts/app/app.component.html', 'hero-detail-1')(format=".")
:marked
  That’s “HTML Plus”.

  Now we start to learn about data binding. The first binding we meet might look like this:

+makeExample('template-syntax/ts/app/app.component.html', 'disabled-button-1')(format=".")
:marked
  We’ll get to that peculiar bracket notation in a moment. Looking beyond it,
  our intuition tells us that we’re binding to the button's `disabled` attribute and setting
  it to the current value of the component’s `isUnchanged` property.

  Our intuition is wrong! Our everyday HTML mental model is misleading us.
  In fact, once we start data binding, we are no longer working with HTML *attributes*. We aren't setting attributes.
  We are setting the *properties* of DOM elements, components, and directives.

.l-sub-section
  :marked
    ### HTML Attribute vs. DOM Property

    The distinction between an HTML attribute and a DOM property is crucial to understanding how Angular binding works.

    **Attributes are defined by HTML. Properties are defined by DOM (the Document Object Model).**

    * A few HTML attributes have 1:1 mapping to properties. `id` is one example.

    * Some HTML attributes don't have corresponding properties. `colspan` is one example.

    * Some DOM properties don't have corresponding attributes. `textContent` is one example.

    * Many HTML attributes appear to map to properties ... but not the way we think!

    That last category can be especially confusing ... until we understand this general rule:

    **Attributes *initialize* DOM properties and then they are done.
    Property values may change; attribute values don't.**

    For example, when the browser renders `<input type="text" value="Bob">`, it creates a
    corresponding DOM node with a `value` property *initialized* to "Bob".

    When the user enters "Sally" into the input box, the DOM element `value` *property* becomes "Sally".
    But the HTML `value` *attribute* remains unchanged as we discover if we ask the input element
    about that attribute: `input.getAttribute('value') // returns "Bob"`

    The HTML attribute `value` specifies the *initial* value; the DOM `value` property is the *current* value.

    The `disabled` attribute is another peculiar example. A button's `disabled` *property* is
    `false` by default so the button is enabled.
    When we add the `disabled` *attribute*, it's presence alone initializes the  button's `disabled` *property* to `true`
    so the button is disabled.

    Adding and removing the `disabled` *attribute* disables and enables the button. The value of the *attribute* is irrelevant
    which is why we cannot enable a button by writing `<button disabled="false">Still Disabled</button>`.

    Setting the button's `disabled` *property*  (e.g. with an Angular binding) disables or enables the button.
    The value of the *property* matters.

    **The HTML attribute and the DOM property are not the same thing even when they have the same name.**

:marked
  This is so important, we’ll say it again.

  **Template binding works with *properties* and *events*, not *attributes*.**

.callout.is-helpful
  header A world without attributes
  :marked
    In the world of Angular 2, the only role of attributes is to initialize element and directive state.
    When we data bind, we're dealing exclusively with element and directive properties and events.
    Attributes effectively disappear.
:marked
  With this model firmly in mind, we are ready to discuss the variety of target properties to which we may bind.

  ### Binding Targets
  The **target of a data binding** is something in the DOM.
  Depending on the binding type, the target can be an
  (element | component | directive) property, an
  (element | component | directive) event, or (rarely) an attribute name.
  The following table summarizes:

<div width="90%">
table
  tr
    th Binding Type
    th Target
    th Examples
  tr
    td Property
    td.
      Element&nbsp;Property<br>
      Component&nbsp;Property<br>
      Directive&nbsp;property
    td
      +makeExample('template-syntax/ts/app/app.component.html', 'property-binding-syntax-1')(format=".")
  tr
    td Event
    td.
      Element&nbsp;Event<br>
      Component&nbsp;Event<br>
      Directive&nbsp;Event
    td
      +makeExample('template-syntax/ts/app/app.component.html', 'event-binding-syntax-1')(format=".")
  tr
    td Two-way
    td.
      Directive&nbsp;Event
      Property
    td
      +makeExample('template-syntax/ts/app/app.component.html', '2-way-binding-syntax-1')(format=".")
  tr
    td Attribute
    td.
      Attribute
      (the&nbsp;exception)
    td
      +makeExample('template-syntax/ts/app/app.component.html', 'attribute-binding-syntax-1')(format=".")
  tr
    td Class
    td.
      <code>class</code> Property
    td
      +makeExample('template-syntax/ts/app/app.component.html', 'class-binding-syntax-1')(format=".")
  tr
    td Style
    td.
      <code>style</code> Property
    td
      +makeExample('template-syntax/ts/app/app.component.html', 'style-binding-syntax-1')(format=".")
</div>

:marked
  Let’s descend from the architectural clouds and look at each of these binding types in concrete detail.

.l-main-section
:marked
  ## Property Binding
  We write a template **Property Binding** when we want to set a property of a view element to the value of 
  a [template expression](#template-expressions).

  The most common Property Binding sets an element property to a component property value as when
  we bind the source property of an image element to the component’s `heroImageUrl` property.
+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-1')(format=".")
:marked
  … or disable a button when the component says that it `isUnchanged`.
+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-2')(format=".")
:marked
  … or set a property of a directive
+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-3')(format=".")
:marked
  … or set the model property of a custom component (a great way
  for parent and child components to communicate)
+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-4')(format=".")
:marked
  ### One-way *in*
  People often describe property binding as *one way data binding* because it flows a value in one direction, 
  from a component’s data property into a target element property.
  
  We cannot use property binding to pull values *out* of the target element.
  We can't bind to a property of the target element to read it. We can only set it.

.l-sub-section
  :marked
    Nor can we use property binding to *call* a method on the target element.
    
    If the element raises events we can listen to them with an [event binding](#event-binding).
    
    If we must read a target element property or call one of its methods,
    we'll need a different technique. 
    See the API reference for 
    [viewChild](../api/core/ViewChild-var.html) and 
    [contentChild](../api/core/ContentChild-var.html).

:marked
  ### Binding Target
  A name between enclosing square brackets identifies the target property. The target property in this example is the image element’s `src` property.

+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-1')(format=".")
:marked
  Some developers prefer the `bind-` prefix alternative, known as the “canonical form”:
+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-5')(format=".")
:marked
  The target name is always the name of a property, even when it appears to be the name of something else. We see `src` and may think it’s the name of an attribute. No. It’s the name of an image element property.

  Element properties may be the more common targets,
  but Angular looks first to see if the name is a property of a known directive
  as it is in the following example:
+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-3')(format=".")

.l-sub-section
  :marked
    Technically, Angular is matching the name to a directive [input](#inputs-outputs),
    one of the property names listed in the directive’s `inputs` array or a property decorated with `@Input()`.
    Such inputs map to the directive’s own properties.
:marked
  If the name fails to match a property of a known directive or element, Angular reports an “unknown directive” error.

  ### Property Binding template expressions
  Evaluation of the expression should have no visible side-effects. The expression language itself does its part to keep us safe. We can’t assign a value to anything in a Property Binding expression nor use the increment and decorator operators.

  Of course, our expression might invoke a property or method that has side-effects. Angular has no way of knowing that or stopping us.

  The expression could call something like `getFoo()`. Only we know what `getFoo()` does.
  If `getFoo()`  changes something and we happen to be binding to that something, we risk an unpleasant experience. Angular may or may not display the changed value. Angular may detect the change and throw a warning error. Our general advice: stick to data properties and methods that return values and do no more.

  The template expression should evaluate to a value of the type expected by the target property. Most native element properties do expect a string. The image `src` should be set to a string, an URL for the resource providing the image. On the other hand, the `disabled` property of a button expects a Boolean value so our expression should evaluate to `true` or `false`.

  The `hero` property of the `HeroDetail` component expects a `Hero` object which is exactly what we’re sending in the Property Binding:
+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-4')(format=".")
:marked
  This is good news for the Angular developer.
  If `hero` were an attribute we could not set it to a `Hero` object.
+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-6')(format=".")
:marked
  We can't set an attribute to an object. We can only set it to a string.
  Internally, the attribute may be able to convert that string to an object before setting the like-named element property.
  That’s good to know but not helpful to us when we're trying to pass a significant data object
  from one component element to another.
  The power of Property Binding is its ability to bypass the attribute and
  set the element property directly with a value of the appropriate type.

  ### Property Binding or Interpolation?
  We often have a choice between Interpolation and Property Binding. The following binding pairs do the same thing

+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-vs-interpolation')(format=".")
:marked
  Interpolation is actually a convenient alternative for Property Binding in many cases.
  In fact, Angular  translates those Interpolations into the corresponding Property Bindings
  before rendering the view.

  There is no technical reason to prefer one form to the other.
  We lean toward readability which tends to favor interpolation.
  We suggest establishing coding style rules for the organization and choosing the form that
  both conforms to the rules and feels most natural for the task at hand.

.l-main-section
:marked
  <a id="other-bindings"></a>
  ## Attribute, Class, and Style Bindings
  The template syntax provides specialized one-way bindings for scenarios less well suited to Property Binding.

  ### Attribute Binding
  We can set the value of an attribute directly with an **Attribute Binding**.
.l-sub-section
  :marked
    This is the only exception to the rule that a binding sets a target property. This is the only binding that creates and sets an attribute.

:marked
  We have stressed throughout this chapter that setting an element property with a Property Binding is always preferred to setting the attribute with a string. Why does Angular offer Attribute Binding?

  **We must use Attribute Binding when there is no element property to bind.**

  Consider the [aria](https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA),
  [svg](https://developer.mozilla.org/en-US/docs/Web/SVG), and
  table span attributes. They are pure attributes.
  They do not correspond to element properties and they do not set element properties.
  There are no property targets to bind to.

  We become painfull aware of this fact when we try to write something like this:
code-example(language="html").
  &lt;tr>&lt;td colspan="{{1 + 1}}">Three-Four&lt;/td>&lt;/tr>
:marked
  … and get the error:
code-example(format="", language="html").
  Template parse errors:
  Can't bind to 'colspan' since it isn't a known native property
:marked
  As the message says, the `<td>` element does not have a `colspan` property.
  It has the "colspan" *attribute* but
  interpolation and property binding can only set properties, not attributes.

  We need an Attribute Binding to create and bind to such attributes.

  Attribute Binding syntax resembles Property Binding.
  Instead of an element property between brackets, we start with the keyword **`attr`**
  followed by the name of the attribute and then set it with an expression that resolves to a string.

  Here we bind `[attr.colspan]` to a calulated value:
+makeExample('template-syntax/ts/app/app.component.html', 'attrib-binding-colspan')(format=".")
:marked
  Here's how the table renders:
  <table border="1px">
    <tr><td colspan="2">One-Two</td></tr>
    <tr><td>Five</td><td>Six</td></tr>
   </table>

  One of the primary use cases for the Attribute Binding
  is to set aria attributes as we see in this example
+makeExample('template-syntax/ts/app/app.component.html', 'attrib-binding-aria')(format=".")
:marked
  ### Class Binding

  We can add and remove CSS class names from an element’s `class` attribute with the **Class Binding**.

  Class Binding syntax resembles Property Binding.
  Instead of an element property between brackets, we start with the keyword `class` followed
  by the name of a CSS class: `[class.class-name]`.

  In the following examples we see how to add and remove the application's "special" class
  with class bindings.  We start by setting the attribute without binding:
+makeExample('template-syntax/ts/app/app.component.html', 'class-binding-1')(format=".")
:marked
  We replace that with a binding to a string of the desired class names; this is an all-or-nothing, replacement binding.
+makeExample('template-syntax/ts/app/app.component.html', 'class-binding-2')(format=".")
:marked
  Finally, we bind to a specific class name.
  Angular adds the class when the template expression evaluates to something truthy and
  removes the class name when the expression is falsey.
+makeExample('template-syntax/ts/app/app.component.html', 'class-binding-3')(format=".")

.l-sub-section
  :marked
    While this is a fine way to toggle a single class name,
    we generally prefer the [NgClass directive](#ngClass) for managing multiple class names at the same time.

:marked
  ### Style Binding

  We can set inline styles with a **Style Binding**.

  Style Binding syntax resembles Property Binding.
  Instead of an element property between brackets, we start with the key word `style`
  followed by the name of a CSS style property: `[style.style-property]`.

+makeExample('template-syntax/ts/app/app.component.html', 'style-binding-1')(format=".")
:marked
  Some Style Binding styles have unit extension. Here we conditionally set the `fontSize` in  “em” and “%” units .
+makeExample('template-syntax/ts/app/app.component.html', 'style-binding-2')(format=".")

.l-sub-section
  :marked
    While this is a fine way to set a single style,
    we generally prefer the [NgStyle directive](#ngStyle) when setting several inline styles at the same time.

.l-main-section
:marked
  ## Event Binding
  The bindings we’ve met so far flow data in one direction *from the component to an element*.

  Users don’t just stare at the screen. They enter text into a input box. They pick items from a list.
  They click buttons. Such user actions may result in a flow of data in the opposite direction,
  ***from an element to the component***.

  The only way to know about a user action is to listen for certain events such as
  keystrokes, mouse movements, clicks and touches.
  We declare our interest in user actions through Angular Event Binding.

  Event Binding syntax consists of a target event within parentheses on the left of an equal sign and a quoted
  [**template statement**](#template-statements) on the right.
  
  The following Event Binding listens for the button’s click event and calls the component's `onSave()` method:
+makeExample('template-syntax/ts/app/app.component.html', 'event-binding-1')(format=".")
:marked
  ### Binding target
  A **name between enclosing parentheses** identifies the target event. In the following example, the target is the button’s click event.
+makeExample('template-syntax/ts/app/app.component.html', 'event-binding-1')(format=".")
:marked
  Some developers prefer the `on-` prefix alternative, known as the “canonical form”:
+makeExample('template-syntax/ts/app/app.component.html', 'event-binding-2')(format=".")
:marked
  Element events may be the more common targets, but Angular looks first to see if the name matches an event property
  of a known directive as it does in the following example:
+makeExample('template-syntax/ts/app/app.component.html', 'event-binding-3')(format=".")
:marked
  If the name fails to match an element event or an output property of a known directive,
  Angular reports an “unknown directive” error.

  ### $event and event handling statements
  In an Event Binding, Angular sets up an event handler for the target event.

  When the event is raised, the handler executes the template statement.
  The template statement typically involves a receiver that wants to do something
  in response to the event such as take a value from the HTML control and store it
  in a model.

  The binding conveys information about the event including data values through
  an **event object named `$event`**.

  The shape of the $event object is determined by the target event itself.
  If the target event is a native DOM element event, the `$event` is a
  [DOM event object]( https://developer.mozilla.org/en-US/docs/Web/Events) with properties such as `target` and `target.value`.

  Consider this example:
+makeExample('template-syntax/ts/app/app.component.html', 'without-NgModel')(format=".")
:marked
  We’re binding the input box `value` to a `firstName` property and we’re listening for changes by binding to the input box’s `input` event.
  When the user makes changes, the `input` event is raised, and the binding executes the statement within a context that includes the DOM event object, `$event`.

  We must follow the `$event.target.value` path to get the changed text so we can update the `firstName`

  If the event belongs to a directive (remember: components are directives), `$event` has whatever shape the directive chose to produce.
  Consider a `HeroDetailComponent` that produces `deleted` events with an `EventEmitter`.
+makeExample('template-syntax/ts/app/hero-detail.component.ts', 'deleted', 'HeroDetailComponent.ts (excerpt)')(format=".")
:marked
  When something invokes the `onDeleted()` method, we "emit" a `Hero` object.

  Now imagine a parent component that listens for that event with an Event Binding.
+makeExample('template-syntax/ts/app/app.component.html', 'event-binding-to-component')(format=".")
:marked
  The event binding surfaces the *hero-to-delete* emitted by `HeroDetail` to the statement via the `$event` variable.
  We pass it along to the parent `onHeroDeleted()` method.
  That method presumably knows how to delete the hero.

  Evaluation of this Event Binding template statement has a side-effect. It deletes a hero.
  Side-effects are not just OK; they are expected.

  The statement could update the model thereby triggering other changes that percolate through the system, changes that
  are ultimately displayed in this view and other views.
  The event processing may result in queries and saves to a remote server. It's all good.

  ### Event bubbling and propagation
  Angular invokes the event-handling statement if the event is raised by the current element or one of its child elements.
+makeExample('template-syntax/ts/app/app.component.html', 'event-binding-bubbling')(format=".")
:marked
  Many DOM events, both [native](https://developer.mozilla.org/en-US/docs/Web/Guide/Events/Overview_of_Events_and_Handlers ) and [custom](https://developer.mozilla.org/en-US/docs/Web/Guide/Events/Creating_and_triggering_events ),  “bubble” events up their ancestor tree of DOM elements until an event handler along the way prevents further propagation.

.l-sub-section
  :marked
    `EventEmitter` events don’t bubble.

:marked
  The result of an Event Binding statement determines if
  [event propagation](https://developer.mozilla.org/en-US/docs/Web/API/Document_Object_Model/Examples#Example_5:_Event_Propagation)
  continues or stops with the current element.

  Event propagation stops if the binding statement returns a falsey value (as does a method with no return value).
  Clicking the button in this next example triggers a save;
  the click doesn't make it to the outer `<div>` so it's save is not called:
+makeExample('template-syntax/ts/app/app.component.html', 'event-binding-no-propagation')(format=".")
:marked
  Propagation continues if the statement returns a truthy value. The click is heard both by the button
  and the outer `<div>`, causing a double save:
+makeExample('template-syntax/ts/app/app.component.html', 'event-binding-propagation')(format=".")


.l-main-section
:marked
  <a name="ngModel"></a>
  ## Two-Way Binding with NgModel
  When developing data entry forms we often want to both display a data property and update that property when the user makes changes.

  The `NgModel` directive serves that purpose as seen in this example:
+makeExample('template-syntax/ts/app/app.component.html', 'NgModel-1')(format=".")
.callout.is-important
  header 
    :marked
       <span style="font-family:consolas; monospace">[()]</span> = banana in a box
  :marked
    To remember that the parentheses go inside the brackets, visualize a *banana in a box*.
:marked
  If we prefer the “canonical” prefix form to the punctuation form, we can write
+makeExample('template-syntax/ts/app/app.component.html', 'NgModel-2')(format=".")
:marked
  There’s a story behind this construction, a story that builds on the Property and Event Binding techniques we learned previously.

  We could have achieved the same result as `NgModel` with separate bindings to the
  the `<input>` element's  `value` property and `input` event.
+makeExample('template-syntax/ts/app/app.component.html', 'without-NgModel')(format=".")
:marked
  That’s cumbersome. Who can remember what element property to set and what event reports user changes?
  How do we extract the currently displayed text from the input box so we can update the data property?
  Who wants to look that up each time?

  That `ngModel` directive hides these onerous details. It wraps the element’s `value` property, listens to the `input` event,
  and raises its own event with the changed text ready for us to consume.
+makeExample('template-syntax/ts/app/app.component.html', 'NgModel-3')(format=".")
:marked
  That’s an improvement. It should be better.

  We shouldn't have to mention the data property twice. Angular should be able to read the component’s data property and set it
  with a single declaration &mdash; which it can with the `[( )]` syntax:
+makeExample('template-syntax/ts/app/app.component.html', 'NgModel-1')(format=".")

.l-sub-section
  :marked
    Internally, Angular maps the term, `ngModel`, to an `ngModel` input property and an
    `ngModelChange` output property.
    That’s a specific example of a more general pattern in which it matches `[(x)]` to an `x` input property
    for Property Binding and an `xChange` output property for Event Binding.

    We can write our own two-way binding directive that follows this pattern if we're ever in the mood to do so.
:marked
  Is `[(ngModel)]` all we need? Is there ever a reason to fall back to its expanded form?

  Well `NgModel` can only set the target property.
  What if we need to do something more or something different when the user changes the value?

  Let's try something silly like forcing the input value to uppercase.
+makeExample('template-syntax/ts/app/app.component.html', 'NgModel-4')(format=".")
:marked
  Here are all variations in action, including the uppercase version:
figure.image-display
    img(src='/resources/images/devguide/template-syntax/ng-model-anim.gif' alt="NgModel variations")
:marked

.l-main-section
:marked
  <a name="directives"></a>
  ## Built-in Directives

  Earlier versions of Angular included over seventy built-in directives.
  The community contributed many more and individuals have created countless private directives for internal applications.

  We don’t need many of those directives in Angular 2.
  Quite often we can achieve the same results with the more capable and expressive Angular 2 binding system.
  Why create a directive to handle a click when we can write a simple binding such as this?
+makeExample('template-syntax/ts/app/app.component.html', 'event-binding-1')(format=".")
:marked
  We still benefit from directives that simplify complex tasks.
  Angular still ships with built-in directives; just not as many.
  We will write our own directives; just not as many.

  In this segment we review some of the most frequently used built-in directives.

<a id="ngClass"></a>
.l-main-section
:marked
  ### NgClass

  We typically control how elements appear
  by adding and removing CSS classes dynamically.
  We can bind to `NgClass` to add or remove several classes simultaneously.

  We prefer to use a [Class Binding](#class-binding) to add or remove a *single* class.
+makeExample('template-syntax/ts/app/app.component.html', 'class-binding-3a')(format=".")
:marked
  The `NgClass` directive may be the better choice
  when we want to add or remove *many* classes at the same time.

  Our favorite way to apply `NgClass` is by binding it to a key:value control object. Each key of the object is a class name and its value is `true` if the class should be added, `false` if it should be removed.

  Consider a component method such as `setClasses` that returns its approval of two class names:
+makeExample('template-syntax/ts/app/app.component.ts', 'setClasses')(format=".")
:marked
  Now add an `NgClass` property binding to call it like this
+makeExample('template-syntax/ts/app/app.component.html', 'NgClass-1')(format=".")

<a id="ngStyle"></a>
.l-main-section
:marked
  ### NgStyle
  We may set inline styles dynamically based on the state of the component.
  We bind to `NgStyle` to set many inline styles simultaneously.

  We prefer to use a [Style Binding](#style-binding) to set a *single* style value.
+makeExample('template-syntax/ts/app/app.component.html', 'NgStyle-1')(format=".")
:marked
  The `NgStyle` directive may be the better choice
  when we want to set *many* inline styles at the same time.

  We apply `NgStyle` by binding it to a key:value control object.
  Each key of the object is a style name and its value is whatever is appropriate for that style.

  Consider a component method such as `setStyles` that returns an object defining three styles:
+makeExample('template-syntax/ts/app/app.component.ts', 'setStyles')(format=".")
:marked
  Now add an `NgStyle` property binding to call it like this
+makeExample('template-syntax/ts/app/app.component.html', 'NgStyle-2')(format=".")
:marked
  Alternatively, we can return an object with camelCase style property names with the same effects:
+makeExample('template-syntax/ts/app/app.component.ts', 'setStyles2')(format=".")
:marked

<a id="ngIf"></a>
.l-main-section
:marked
  ### NgIf
  We can add an element sub-tree (an element and its children) to the DOM  by binding an `NgIf` directive to a truthy expression.
+makeExample('template-syntax/ts/app/app.component.html', 'NgIf-1')(format=".")

.alert.is-critical
  :marked
    The leading asterisk (\*) in front of `ngIf` is a critical part of this syntax.
    See the section below on [\* and &lt;template>](#star-template).
:marked
  Binding to a falsey expression removes the element sub-tree from the DOM.
+makeExample('template-syntax/ts/app/app.component.html', 'NgIf-2')(format=".")
:marked
  #### Visibility and NgIf are not the same
  We can show and hide an element sub-tree (the element and its children) with a  [Class](#class-binding) or a [Style](#style-binding) binding:
+makeExample('template-syntax/ts/app/app.component.html', 'NgIf-3')(format=".")
:marked
  Hiding a sub-tree is quite different from excluding a sub-tree with `NgIf`.

  When we hide the element sub-tree, it remains in the DOM.
  Components in the sub-tree are preserved along with their state.
  Angular may continue to check for changes even to invisible properties.
  The sub-tree may tie up substantial memory and computing resources.

  When `NgIf` is `false`, Angular physically removes the element sub-tree from the DOM.
  It destroys components in the sub-tree along with their state which may free up substantial resources
  resulting in better performance for the user.

  The show/hide technique is probably fine for small element trees.
  We should be wary when hiding large trees; `NgIf` may be the safer choice. Always measure before leaping to conclusions.

<a id="ngSwitch"></a>
.l-main-section
:marked
  ### NgSwitch
  We bind to `NgSwitch` when we want to display *one* element tree (an element and its children)
  from a *set* of possible element trees based on some condition.
  Angular only puts the *selected* element tree into the DOM.

  Here’s an example:
+makeExample('template-syntax/ts/app/app.component.html', 'NgSwitch')(format=".")
:marked
  We bind the parent `NgSwitch` directive to an expression returning a “switch value”.  The value is a string in this example but it can be a value of any type.

  The parent `NgSwitch` directive controls a set of child`<template>` elements. Each `<template>` wraps a candidate subtree. A template is either pegged to a “match value” expression or marked as the default template.

  **At any particular moment, only one of these templates will be rendered**

  If the template’s “match value” equals the “switch value”, Angular adds the template’s sub-tree to the DOM. If no template is a match and there is a default template, Angular adds the default template’s sub-tree to the DOM. Angular removes and destroys the sub-tree’s of all other templates.

  There are three collaborating directives at work here.
  1. `ngSwitch` - bound to an expression that returns the switch value.
  1. `ngSwitchWhen` - bound to an expression returning a match value.
  1. `ngSwitchDefault` - a marker attribute on the default template.

<a id="ngFor"></a>
.l-main-section
:marked
  ### NgFor
  `NgFor` is a “repeater” directive. It will be familiar if we’ve written repeaters for other view engines.

  Our goal is to present a list of items. We define a block of HTML that defines how a single item should be displayed.
  We tell Angular to use that block as a template for rendering each item in the list.

  Here is an example of `NgFor` applied to a simple `<div>`.
+makeExample('template-syntax/ts/app/app.component.html', 'NgFor-1')(format=".")
:marked
  We can apply an `NgFor` to a component element as well as we do in this example:
+makeExample('template-syntax/ts/app/app.component.html', 'NgFor-2')(format=".")

.alert.is-critical
  :marked
    The leading asterisk (\*) in front of `ngFor` is a critical part of this syntax.
    See the section below on [\* and &lt;template>](#star-template).
:marked
  The text assigned to `*ngFor` is the instruction that guides the repeater process.

.l-sub-section
  :marked
    #### NgFor Micro-syntax
    The string assigned to `*ngFor` is not a [template expression](#template-expressions).
    It’s a little language of its own called a “micro-syntax” that Angular interprets. In this example it means:

    >*Take each hero in the `heroes` array, store it in the local `hero` variable, and make it available to the templated HTML
    for each iteration*.

    Angular translates this instruction into a new set of elements and bindings.
    We’ll talk about this in the next section about templates.
:marked
  In our two examples, the `ngFor` directive iterates over the `heroes` array returned by the parent component’s `heroes` property
  and stamps out instances of the element to which it is applied.
  Angular creates a fresh instance of the template for each hero in the array.

  The (#) character before "hero" identifies a [local template variable](#local-vars) called `hero`.

  We reference this variable within the template to access a hero’s properties as we’re doing in the interpolation
  or we can pass it in a binding to a component element as we're doing with `hero-detail`.

  #### NgFor with index
  The `ngFor` directive supports an optional index that increases from 0 to the length of the array for each iteration.
  We can capture that in another local template variable (`i`) and use it in our  template too.

  This next example stamps out rows that display like "1 - Hercules Son of Zeus":

+makeExample('template-syntax/ts/app/app.component.html', 'NgFor-3')(format=".")
:marked
.l-sub-section
  :marked
    Learn about other special values such as `last`, `even` and `odd` in the [API](../api/common/NgFor-directive.html) guide.

<a name="star-template"></a>
<a name="structural-directive"></a>
.l-main-section
:marked
  ## * and &lt;template>
  When we reviewed the `ngFor` and `ngIf` built-in directives we called out an oddity of the syntax, the asterisk (*)  that appears before the directive name.

  This is a bit of “**syntactic sugar**” that makes it easier to read and write directives that modify HTML layout
  with the help of templates.
  `NgFor`, `NgIf`, and `NgSwitch` all add and remove element subtrees that are wrapped in `<template>` tags.

  With the [NgSwitch](#ngSwitch) directive we always write the `<template>` tags explicitly as we saw [above](#ngSwitch).
  There isn’t much choice; we define a different template for each switch choice
  and let the directive render the template that matches the switch value.

  [NgFor](#ngFor) and [NgIf](#ngIf) only need one template,
  the *template-to-repeat* and the *template-to-include* respectively.

  The (\*) prefix syntax is a convenient way for developers to skip the `<template>` wrapper tags and
  focus directly on the HTML element to repeat or include.
  Angular sees the (*) and expands the HTML into the `<template>` tags for us.

  ### Expanding `*ngIf`
  We can do that ourselves if we wish. Instead of writing ...
+makeExample('template-syntax/ts/app/app.component.html', 'Template-1')(format=".")
:marked
  … we can write:
+makeExample('template-syntax/ts/app/app.component.html', 'Template-2')(format=".")
:marked
  Notice the (\*) is gone and we have a [Property Binding](#property-binding) to the `ngIf`
  directive, applied in this case to the `<template>` rather than
  the application’s `hero-detail` component.

  The `[hero]="currentHero"` binding remains on the child `<hero-detail>`
  element inside the template. Angular does that too.


.callout.is-critical
  header Remember the brackets!
  :marked
    Don’t make the mistake of writing `ngIf="currentHero"`!
    That syntax assigns the *string* value, "currentHero", to `ngIf`.
    In JavaScript a non-empty string is a truthy value so `ngIf` would always be
    `true` and Angular will always display the `hero-detail`
    … even when there is no `currentHero`!

:marked
  ### Expanding `*ngFor`
  A similar transformation applies to `*ngFor`. We can "de-sugar" the syntax ourselves and go from ...
+makeExample('template-syntax/ts/app/app.component.html', 'NgFor-2')(format=".")
:marked
  ... to
+makeExample('template-syntax/ts/app/app.component.html', 'Template-3')(format=".")
:marked
  ... and from there to
+makeExample('template-syntax/ts/app/app.component.html', 'Template-4')(format=".")
:marked
  This is a bit more complex than `NgIf` because a repeater has more moving parts to configure.
  In this case, we have to remember the `NgForOf` directive that identifies the list.
  It should be clear why we prefer the `*ngFor` syntax to writing out this expanded HTML ourselves.

<a id="local-vars"></a>
.l-main-section
:marked
  ## Local template variables

  A **local template variable** is a vehicle for moving data across element lines.

  We've seen the `#hero` local template variable several times in this chapter,
  most prominently when writing [NgFor](#ngFor) repeaters.

  In the [* and &lt;templates>](#star-template) segment we learned how Angular expands
  an `*ngFor` on a component tag into a `<template>` that wraps the component.
+makeExample('template-syntax/ts/app/app.component.html', 'Template-4')(format=".")
:marked
  The (#) prefix character in front of "hero" means that we're defining a `hero` variable.
.l-sub-section
  :marked
    Some folks don't like the (#) character.
    The `var-` prefix is the  “cannonical” alternative to "#". We could have declared our variable as `var-hero`.
:marked
  We defined `hero` on the outer `<template>` element where it becomes the current hero item
  as Angular iterates through the list of heroes.

  The `hero` variable appears again in the binding on the inner `<hero-detail>` component element.
  That's how each instance of the `<hero-detail>` gets its hero.

  ### Referencing a local template variable

  We can reference a local template variable on the same element, on a sibling element, or on
  any of its child elements.

  Here are two other examples of creating and consuming a local template variable:
+makeExample('template-syntax/ts/app/app.component.html', 'var-phone')(format=".")
:marked
  ### How it gets its value
  The value assigned to the variable depends upon the context.

  When a directive is present on the element, as it is in the earlier NgFor `<hero-detail>` component example,
  the directive sets the value.  Accordingly, the `NgFor` directive
  sets the `hero` variable to a hero item from the `heroes` array.

  When there is no directive present, as in phone and fax examples,
  Angular sets the variable to the element on which it was defined.
  We defined these variables on the `input` elements.
  We’re passing those `input` element objects across to the
  button elements where they become arguments to the `call()` methods in the event bindings.

  ### NgForm and local template variables
  Let's look at one final example, a Form, the poster child for local template variables.

  The HTML for a form can be quite involved as we saw in the [Forms](forms.html) chapter.
  The following is a *simplified* example &mdash; and it's not simple at all.
+makeExample('template-syntax/ts/app/app.component.html', 'var-form')
:marked
  A local template variable, `theForm`, appears three times in this example, separated
  by a large amount of HTML.
+makeExample('template-syntax/ts/app/app.component.html', 'var-form-a')
:marked
  What is the value of `theForm`?

  It would be the [HTMLFormElement](https://developer.mozilla.org/en-US/docs/Web/API/HTMLFormElement)
  if Angular hadn't taken it over.
  It's actually `ngForm`, a reference to the Angular built-in `NgForm` directive that wraps the native `HTMLFormElement`
  and endows it with additional super powers such as the ability to
  track the validity of user input.

  This explains how we can disable the submit button by checking `theForm.form.valid`
  and pass an object with rich information to the parent component's `onSubmit` method.

<a id="inputs-outputs"></a>
.l-main-section
:marked
  ## Input and Output Properties
  We can only bind to **target directive** properties that are either **inputs** or **outputs**.
  
.alert.is-important
  :marked
    A *component is a directive*. We use the terms "directive" and "component" interchangeably.

.l-sub-section
  :marked
    We're drawing a sharp distinction between a data binding **target** and a data binding **source**.

    The *target* of a binding is to the *left* of the (=).
    The *source* is on the *right* of the (=).
    
    The *target* of a binding is the property or event inside the binding punctuation: `[]`, `()` or `[()]`.
    The *source* is either inside quotes (") or within an interpolation (`{}`).

    Every member of a **source** directive or component is automatically available for binding.
    We don't have to do anything special to access a component member in a template expression or statement.

    We have *limited* access to members of a **target** directive or component.
    We can only bind to properties that are explicitly identified as *inputs* and *outputs*.
:marked
  In this chapter we’ve focused mainly on binding to component members within template expressions and statements
  that appear on the *right side of the binding declaration*.
  A member in that position is a binding “data source”.

  In the following example, `iconUrl` and `onSave` are members of the `AppComponent`
  referenced within quoted syntax to the right of the (=).
+makeExample('template-syntax/ts/app/app.component.html', 'io-1')(format=".")
:marked
  They are *neither inputs nor outputs* of `AppComponent`. They are data sources for their bindings.

  Now look at the `HeroDetailComponent` when it is the **target of a binding**.
+makeExample('template-syntax/ts/app/app.component.html', 'io-2')(format=".")
:marked
  Both `HeroDetail.hero` and `HeroDetail.deleted` are on the **left side** of binding declarations.
  `HeroDetail.hero` is inside brackets; it is the target of a Property Binding. 
  `HeroDetail.deleted` is inside parentheses; it is the target of an Event Binding.
  
  ### Declaring input and output properties
  Target properties must be explicitly marked as inputs or outputs.
  
  When we peek inside `HeroDetailComponent` we see that these properties are marked
  with decorators as input and output properties.
+makeExample('template-syntax/ts/app/hero-detail.component.ts', 'input-output-1')(format=".")
:marked
.l-sub-section
  :marked
    Alternatively, we can identify them in the `inputs` and `outputs` arrays
    of the directive metadata as seen in this example:
  +makeExample('template-syntax/ts/app/hero-detail.component.ts', 'input-output-2')(format=".")
  <br>
  :marked
    We can specify an input/output property with a decorator or in one the metadata arrays.
    Don't do both!
:marked
  ### Input or Output?

  *Input* properties usually receive data values.
  *Output* properties expose event producers (e.g, an `EventEmitter`).
  
  The terms "input" and "output" reflect the perspective of the target directive.
  
  `HeroDetail.hero` is an ***input*** property from the perspective of `HeroDetailComponent`
  because data flow  *into* that property from a template binding expression.

  `HeroDetail.deleted` is an ***output*** property from the perspective of `HeroDetailComponent`
  because events stream *out* of that property and toward the handler in a template binding statement.
  
  ### Aliasing input/output properties

  Sometimes we want the public name of an input/output property to be different from the internal name.

  This is frequently the case with [Attribute Directives](attribute-directives.html).
  Directive consumers expect to bind to the name of the directive.
  For example, we expect to bind to the `myClick` event property of the `MyClickDirective`.

  The directive name is often a poor choice for the the internal property name
  because it rarely describes what the property does.
  `myClick` is not a good name for a property that emits click events.

  Fortunately, we can have a public name for the property that meets conventional expectations
  and use a different name internally
  by providing a public alias for the internal property name in the decorator like this:
+makeExample('template-syntax/ts/app/my-click.directive.ts', 'my-click-output-1')(format=".")
:marked
  Now the directive name, `myClick`, is the public facing property name to which we can bind
+makeExample('template-syntax/ts/app/app.component.html', 'my-click')(format=".")
:marked
  while inside the directive, the property is known as `clicks`.
  
  With aliasing we please both the directive consumer and the directive author.
.l-sub-section
  :marked
    We can alias property names in the `inputs` and `outputs` arrays as well.
    We write a colon-delimited string with
    the internal property name on the left and the public name on the right:
  +makeExample('template-syntax/ts/app/my-click.directive.ts', 'my-click-output-2')(format=".")

<a id="expression-operators"></a>
.l-main-section
:marked
  ## Template Expression Operators
  The template expression language employs a subset of JavaScript syntax supplemented with some special operators
  for specific scenarios. We'll cover two of them, "pipe" and "Elvis".

  <a id="pipe"></a>
  ### The Pipe Operator ( | )
  The result of an expression may require some transformation before we’re ready to use it in a binding.  For example, we may wish to display a number as a currency, force text to uppercase, or filter a list and sort it.

  Angular [Pipes](./pipes.html) are a good choice for small transformations such as these.
  Pipes are simple functions that accept an input value and return a transformed value.
  They are easy to apply within template expressions using the **pipe operator ( | )**:
+makeExample('template-syntax/ts/app/app.component.html', 'pipes-1')(format=".")
:marked
  The pipe operator passes the result of an expression on the left to a pipe function on the right.

  We can chain expressions through multiple pipes
+makeExample('template-syntax/ts/app/app.component.html', 'pipes-2')(format=".")
:marked
  And we can configure them too:
+makeExample('template-syntax/ts/app/app.component.html', 'pipes-3')(format=".")
:marked
  The `json` pipe is particular helpful for debugging our bindings:
+makeExample('template-syntax/ts/app/app.component.html', 'pipes-json')(format=".")
:marked
  <a id="elvis"></a>
  ### The Elvis Operator ( ?. ) and null property paths

  The Angular **“Elvis” operator ( ?. )** is a fluent and convenient way to guard against null and undefined values in property paths.
  Here it is, protecting against a view render failure if the `currentHero` is null.
+makeExample('template-syntax/ts/app/app.component.html', 'elvis-2')(format=".")
:marked
  Let’s elaborate on the problem and this particular solution.

  What happens when the following data bound `title` property is null?
+makeExample('template-syntax/ts/app/app.component.html', 'elvis-1')(format=".")
:marked
  The view still renders but the displayed value is blank; we see only "`The title is`" with nothing after it.
  That is reasonable behavior. At least the app doesn't crash.

  Suppose the template expression involves a property path as in this next example
  where we’re displaying the `firstName` of a null hero.

code-example(format="" language="html").
  The null hero's name is {{nullHero.firstName}}
:marked
  JavaScript throws a null reference error and so does Angular:
code-example(format="" language="html").
  TypeError: Cannot read property 'firstName' of null in [null]
:marked
  Worse, the *entire view disappears*.

  We could claim that this is reasonable behavior if we believed that the `hero` property must never be null.
  If it must never be null and yet it is null,
  we've made a programming error that should be caught and fixed.
  Throwing an exception is the right thing to do.

  On the other hand, null values in the property path may be OK from time to time,
  especially when we know the data will arrive eventually.

  While we wait for data, the view should render without complaint and
  the null property path should display as blank just as the `title` property does.

  Unfortunately, our app crashes when the `currentHero` is null.

  We could code around that problem with [NgIf](#ngIf)
+makeExample('template-syntax/ts/app/app.component.html', 'elvis-4')(format=".")
:marked
  Or we could try to chain parts of the property path with `&&`, knowing that the expression bails out
  when it encounters the first null.
+makeExample('template-syntax/ts/app/app.component.html', 'elvis-5')(format=".")
:marked
  These approaches have merit but they can be cumbersome, especially if the property path is long.
  Imagine guarding against a null somewhere in a long property path such as `a.b.c.d`.

  The Angular  **“Elvis” operator ( ?. )** is a more fluent and convenient way to guard against nulls in property paths.
  The expression bails out when it hits the first null value.
  The display is blank but the app keeps rolling and there are no errors.
+makeExample('template-syntax/ts/app/app.component.html', 'elvis-6')(format=".")
:marked
  It works perfectly with long property paths too:
  ```
  a?.b?.c?.d
  ```

.l-main-section
:marked
  ## What Next?
  We’ve completed our survey of Template Syntax. Time to put that knowledge to work as we write our own Components and Directives.
-												(docs) Move ToH-pt2 to Jade and break toh-pt1 out of the tutorial index

											
										
										
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+								include ../../../../_includes/_util-fns
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+								:marked
-												(docs) Template Syntax

											
										
										
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+								  # Template Syntax
 								  Our Angular application manages what the user sees and does through the interaction of a Component class instance and its user-facing template.
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-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  Many of us are familiar with the Component/Template duality from our experience with Model-View-Controller or Model-View-ViewModel. In Angular,  the Component plays the part of the Controller/ViewModel and the Template represents the view.
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-												(docs) Template Syntax

											
										
										
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+								  Let’s find out what it takes to write a Template for our view.
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-												(docs) Template Syntax

											
										
										
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+								  We’ll cover these basic elements of Template Syntax
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-												(docs) Template Syntax

											
										
										
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+								  >[HTML](#html)
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-												(docs) Template Syntax

											
										
										
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+								  >[Interpolation](#interpolation)
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-												(docs) Template Syntax

											
										
										
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+								  >[Template expressions](#template-expressions)
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-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
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+								  >[Template statements](#template-statements)
-												(docs) Template Syntax

											
										
										
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+								  >[Binding syntax](#binding-syntax)
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-												(docs) Template Syntax

											
										
										
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+								  >[Property Binding](#property-binding)
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-												(docs) Template Syntax

											
										
										
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+								  >[Attribute, Class and Style Bindings](#other-bindings)
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-												(docs) Template Syntax

											
										
										
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+								  >[Event Binding](#event-binding)
-												chore(jade): upgrade to use `marked` filter

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-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
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+								  >[Two-way data binding with `NgModel`](#ngModel)
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-												(docs) Template Syntax

											
										
										
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+								  >[Built-in Directives](#directives)
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-												(docs) Template Syntax

											
										
										
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+								  >[* and &lt;template>](#star-template)
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-												(docs) overhaul user-input

											
										
										
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+								  >[Local template variables](#local-vars)
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-												(docs) Template Syntax

											
										
										
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+								  >[Input and Output Properties](#inputs-outputs)
-												chore(jade): upgrade to use `marked` filter

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-												(chore) devguide template-syntax - fix broken links
closes #422

											
										
										
											2015-11-30 18:56:37 -05:00
+								  >[Template Expression Operators](#expression-operators)
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
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+								  [Live Example](/resources/live-examples/template-syntax/ts/plnkr.html).
-												(docs) Template Syntax

											
										
										
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 								.l-main-section
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+								:marked
-												(docs) Template Syntax

											
										
										
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+								  ## HTML
 								  HTML is the language of the Angular template. Our “[QuickStart](./quickstart.html)” application had a template that was pure HTML
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'my-first-app')(format=".")
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+								:marked
-												(docs) Template Syntax

											
										
										
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+								  Almost all HTML syntax is valid template syntax. The `<script>` element is a notable exception;  it is forbidden in order to eliminate any possibility of JavaScript injection attacks (in practice it is simply ignored).
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-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  Some legal HTML doesn’t make much sense in a template. The `<html>`, `<body>` and `<base>` elements have no useful role in our repertoire. Pretty much everything else is fair game.
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-												(docs) Template Syntax

											
										
										
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+								  We can extend the HTML vocabulary of our templates with Components and Directives that appear as new elements and attributes. And we are about to learn how to get and set DOM values dynamically through data binding.
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-												(docs) Template Syntax

											
										
										
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+								  Let’s turn to the first form of data binding - interpolation - to see how much richer Template HTML can be.
 								.l-main-section
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+								:marked
-												(docs) Template Syntax

											
										
										
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+								  ## Interpolation
 								  We met the double-curly braces of interpolation, `{{` and `}}`, early in our Angular education.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'first-interpolation')(format=".")
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+								:marked
-												(docs) Template Syntax

											
										
										
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+								  We use interpolation to weave calculated strings into the text between HTML element tags and within attribute assignments.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'title+image')(format=".")
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+								:marked
 								  The material between the braces is often the name of a component property. Angular replaces that name with the
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  string value of the corresponding component property. In this example, Angular evaluates the `title` and `heroImageUrl` properties
 								  and "fills in the blanks", displaying first a bold application title and then a heroic image.
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 								  More generally, the material between the braces is a **template expression** that Angular first **evaluates**
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  and then **converts to a string**. The following interpolation illustrates the point by adding the two numbers within braces:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'sum-1')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								  The expression can invoke methods of the host component as we do here with `getVal()`:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'sum-2')(format=".")
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+								:marked
 								  Angular evaluates all expressions in double curly braces, converts the expression results to strings, and concatenates them with neighboring literal strings. Finally,
 								  it assigns this composite interpolated result to an **element or directive property**.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
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											2015-11-10 13:31:46 -05:00
+								  We appear to be inserting the result between element tags and assigning to attributes.
 								  It's convenient to think so and we rarely suffer for this mistake.
 								  But it is not literally true. Interpolation is actually a special syntax that Angular converts into a
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  [Property Binding](#property-binding) as we explain below. The implications and consequences can be profound.
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  But before we explore that assertion, we’ll take a closer look at template expressions and statements.
-												(docs) Template Syntax

											
										
										
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-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
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+								<a id="template-expressions"></a>
-												(docs) Template Syntax

											
										
										
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+								.l-main-section
-												chore(jade): upgrade to use `marked` filter

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the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
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+								:marked
-												(docs) Template Syntax

											
										
										
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+								  ## Template Expressions
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  A template **expression** produces a value.
 								  Angular executes the expression and assigns it to property of a binding target such
 								  as an HTML element, a component, or a directive.
 								  We put a template expression within the interpolation braces when we wrote `{{1 + 1}}`.
 								  We’ll see template expressions again in [Property Bindings](#property-binding) ,
 								  appearing in quotes to the right of the (=) symbol as in `[property]="expression"`.
 								  We write template expressions in a language that looks like JavaScript.
 								  Many JavaScript expressions are legal template expressions but not all.
 								  JavaScript expressions that have or promote side-effects are prohibited including:
 								  * assignment (`=`)
 								  * the `new` operator
 								  * chaining expressions with `;` or `,`
 								  * increment and decrement operators, `++` and `--`.
 								  Other notable differences from JavaScript syntax include:
 								  * no support for the bit-wise operators, `|` and `&`
 								  * new [template expression operators](#expression-operators), such as `|` and `?.`
 								  <a id="expression-context"></a>
 								  ### Expression Context
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+								  Perhaps more surprising, we cannot refer to anything in the global namespace.
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  We can’t refer to `window` or `document`. We can’t call `console.log` or `Math.max`.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  We are restricted to referencing members of the expression context.
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
 								  The *expression context* is typically the **component instance**, the source of binding values.
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-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
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+								  When we see *title* wrapped in double-curly braces, <code>{{title}}</code>,
 								  we know that `title` is a property of the data-bound component.
 								  When we see *isUnchanged* in `[disabled]="isUnchanged"`,
 								  we know we are referring to that component's `isUnchanged` property.
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 								  The component itself is usually the expression *context* in which case
 								  the template expression usually references that component.
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
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+								  The expression context may include an object other than the component.
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
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+								  A [local template variable](#local-vars) is one such alternative context object.
 								  <a id="no-side-effects"></a>
 								  ### Expression Guidelines
 								  Template expressions can make or break an application.
 								  Please follow these guidelines unless you have an exceptionally good reason to break them
 								  in specific circumstances that you thoroughly understand.
 								  #### No visible side-effects
 								  A template expression should have ***no visible side-effects***.
 								  We're not allowed to change any application state other than the value of the
 								  target property.
 								  This rule is essential to Angular's "unidirectional data flow" policy.
 								  We should never worry that reading a component value might change some other displayed value.
 								  The view should be stable throughout a single rendering pass.
 								  #### Finish fast
 								  Angular executes template expressions more often than we might think.
 								  Expressions should finish quickly or the user experience may drag, especially on slower devices.
 								  #### Keep them simple
 								  Although we can write quite complex template expressions, we strongly discourage that practice.
 								  Most readers frown on JavaScript in the HTML.
 								  A property name or method call should be the norm.
 								  An occasional Boolean negation (`!`) is OK.
 								  Otherwise, confine application and business logic to the component itself where it will be easier to develop and test.
 								  #### Idempotent Expressions
 								  An [idempotent](https://en.wikipedia.org/wiki/Idempotence) expression is ideal because
 								  it is free of side-effects and improves Angular's change detection performance.
 								  In Angular terms, an idempotent expression always returns *exactly the same thing* until
 								  one of its dependent values changes.
 								  Dependent values should not change during a single turn of the JavaScript virtual machine.
 								  If an idempotent expression returns a string or a number, it returns the same string or number
 								  when called twice in a row. If the expression returns an object (including a `Date` or `Array`),
 								  it returns the same object *reference* when called twice in a row.
 								<a id="template-statements"></a>
 								.l-main-section
 								:marked
 								  ## Template Statements
 								  A template **statement** responds to an ***event*** raised by a binding target
 								  such as an element, component, or directive.
 								  We’ll see template statements in [Event Bindings](#event-binding),
 								  appearing in quotes to the right of the (=) symbol as in `(event)="statement"`.
 								  A template statement *has a side-effect*.
 								  It's how we update application state from user input.
 								  There would be no point to responding to an event otherwise.
 								.l-sub-section
 								  :marked
 								    Responding to events is the other side of Angular's "unidirectional data flow".
 								    We're free to change anything, anywhere, during this turn of the JavaScript virtual machine.
 								:marked
 								  Angular template statements are also written in a language that looks like JavaScript.
 								  The template statement parser is different than the template expression parser and
 								  specifically supports both assignment (=) and chaining expressions with semicolons (;) and commas (,).
 								  However, certain JavaScript syntax is not allowed:
 								  * the `new` operator
 								  * increment and decrement operators, `++` and `--`
 								  * bit-wise operators, `|` and `&`
 								  * the [template expression operators](#expression-operators)
 								  As with expressions, we cannot refer to anything in the global namespace.
 								  We can’t refer to `window` or `document`. We can’t call `console.log` or `Math.max`.
 								  We are restricted to referencing members of the statement context.
 								  The **statement context** is typically the **component instance** to which we are binding an event.
 								  The *onSave* in `(click)="onSave()"` is sure to be a method of the data-bound component instance.
 								  The statement context may include an object other than the component.
 								  A [local template variable](#local-vars) is one such alternative context object.
 								  We'll frequently see the reserved `$event` symbol in event binding statements,
 								  representing the "message" or "payload" of the raised event.
-												(docs) Template Syntax

											
										
										
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+								.l-sub-section
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+								  :marked
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								    Although we can write quite complex template statements, we strongly discourage that practice.
 								    Most readers frown on JavaScript in the HTML.
 								    A method call or simple property assignment should be the norm.
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+								:marked
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  Now that we have a feel for template expressions and statements,
 								  we’re ready to learn about the varieties of data binding syntax beyond Interpolation.
-												(docs) Template Syntax

											
										
										
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 								.l-main-section
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+								:marked
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+								  <a id="binding-syntax"></a>
 								  ## Binding syntax overview
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
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+								  Data binding is a mechanism for coordinating what users see with application data values.
 								  While we could push values to and pull values from HTML,
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+								  the application is easier to write, read, and maintain if we turn these chores over to a binding framework.
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
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+								  We simply declare bindings between binding sources and target HTML elements and let the framework do the work.
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+								  Angular provides many kinds of data binding and we’ll discuss each of them in this chapter.
 								  First we'll take a high level view of Angular data binding and its syntax.
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-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
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+								  We can group all bindings into three categories by the direction in which data flows.
 								  Each category has its distinctive syntax:
-												(docs) Template Syntax

											
										
										
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+								table
 								  tr
 								    th Data Direction
 								    th Syntax
 								    th Binding Type
 								  tr
 								    td One way<br>from data source<br>to view target
 								    td
 								      code-example(format="" ).
 								        {{expression}}
 								        [target] = "expression"
 								        bind-target = "expression"
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+								    td.
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+								      Interpolation<br>
 								      Property<br>
 								      Attribute<br>
 								      Class<br>
 								      Style
 								    tr
 								      td One way<br>from view target<br>to data source
 								      td
 								        code-example(format="" ).
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+								          (target) = "statement"
 								          on-target = "statement"
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+								      td Event
 								    tr
 								      td Two way
 								      td
 								        code-example(format="" ).
 								          [(target)] = "expression"
 								          bindon-target = "expression"
 								      td Two-way
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+								:marked
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
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+								  Binding types other than interpolation have a **target name** to the left of the equal sign,
 								  either surrounded by punctuation (`[]`, `()`) or preceded by a prefix (`bind-`, `on-`, `bindon-`).
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 								  What is that target? Before we can answer that question, we must challenge ourselves to look at Template HTML in a new way.
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+								  ### A New Mental Model
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+								  With all the power of data binding and our ability to extend the HTML vocabulary
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+								  with custom markup, it is tempting to think of Template HTML as “HTML Plus”.
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 								  *Well it is HTML Plus*.
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+								  But it’s also significantly different than the HTML we’re used to.
-												(docs) Template Syntax

											
										
										
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+								  We really need a new mental model.
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-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  In the normal course of HTML development, we create a visual structure with HTML elements and
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  we modify those elements by setting element attributes with string constants.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
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+								+makeExample('template-syntax/ts/app/app.component.html', 'img+button')(format=".")
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closes #456

											
										
										
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+								:marked
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+								  We still create a structure and initialize attribute values this way in Angular templates.
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-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
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+								  Then we learn to create new elements with Components that encapsulate HTML
 								  and drop them into our templates as if they were native HTML elements
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
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+								+makeExample('template-syntax/ts/app/app.component.html', 'hero-detail-1')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
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+								:marked
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+								  That’s “HTML Plus”.
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closes #456

											
										
										
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+								  Now we start to learn about data binding. The first binding we meet might look like this:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
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+								+makeExample('template-syntax/ts/app/app.component.html', 'disabled-button-1')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
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+								:marked
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+								  We’ll get to that peculiar bracket notation in a moment. Looking beyond it,
-												(docs) Template Syntax

											
										
										
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+								  our intuition tells us that we’re binding to the button's `disabled` attribute and setting
 								  it to the current value of the component’s `isUnchanged` property.
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 								  Our intuition is wrong! Our everyday HTML mental model is misleading us.
 								  In fact, once we start data binding, we are no longer working with HTML *attributes*. We aren't setting attributes.
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  We are setting the *properties* of DOM elements, components, and directives.
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+								.l-sub-section
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+								  :marked
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+								    ### HTML Attribute vs. DOM Property
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+								    The distinction between an HTML attribute and a DOM property is crucial to understanding how Angular binding works.
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+								    **Attributes are defined by HTML. Properties are defined by DOM (the Document Object Model).**
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+								    * A few HTML attributes have 1:1 mapping to properties. `id` is one example.
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+								    * Some HTML attributes don't have corresponding properties. `colspan` is one example.
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+								    * Some DOM properties don't have corresponding attributes. `textContent` is one example.
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+								    * Many HTML attributes appear to map to properties ... but not the way we think!
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+								    That last category can be especially confusing ... until we understand this general rule:
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 								    **Attributes *initialize* DOM properties and then they are done.
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+								    Property values may change; attribute values don't.**
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+								    For example, when the browser renders `<input type="text" value="Bob">`, it creates a
 								    corresponding DOM node with a `value` property *initialized* to "Bob".
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+								    When the user enters "Sally" into the input box, the DOM element `value` *property* becomes "Sally".
 								    But the HTML `value` *attribute* remains unchanged as we discover if we ask the input element
 								    about that attribute: `input.getAttribute('value') // returns "Bob"`
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+								    The HTML attribute `value` specifies the *initial* value; the DOM `value` property is the *current* value.
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+								    The `disabled` attribute is another peculiar example. A button's `disabled` *property* is
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+								    `false` by default so the button is enabled.
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+								    When we add the `disabled` *attribute*, it's presence alone initializes the  button's `disabled` *property* to `true`
 								    so the button is disabled.
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+								    Adding and removing the `disabled` *attribute* disables and enables the button. The value of the *attribute* is irrelevant
 								    which is why we cannot enable a button by writing `<button disabled="false">Still Disabled</button>`.
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The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) forms - code maintained by _examples
Includes template-syntax.jade clarification on attributes v properties

											
										
										
											2015-10-20 19:10:44 -04:00
+								    Setting the button's `disabled` *property*  (e.g. with an Angular binding) disables or enables the button.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								    The value of the *property* matters.
-												(docs) forms - code maintained by _examples
Includes template-syntax.jade clarification on attributes v properties

											
										
										
											2015-10-20 19:10:44 -04:00
+								    **The HTML attribute and the DOM property are not the same thing even when they have the same name.**
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
 								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  This is so important, we’ll say it again.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  **Template binding works with *properties* and *events*, not *attributes*.**
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								.callout.is-helpful
 								  header A world without attributes
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The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  :marked
 								    In the world of Angular 2, the only role of attributes is to initialize element and directive state.
 								    When we data bind, we're dealing exclusively with element and directive properties and events.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								    Attributes effectively disappear.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
 								  With this model firmly in mind, we are ready to discuss the variety of target properties to which we may bind.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ### Binding Targets
 								  The **target of a data binding** is something in the DOM.
-												chore(jade): upgrade to use `marked` filter

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the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  Depending on the binding type, the target can be an
 								  (element | component | directive) property, an
 								  (element | component | directive) event, or (rarely) an attribute name.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  The following table summarizes:
 								<div width="90%">
 								table
 								  tr
 								    th Binding Type
 								    th Target
 								    th Examples
 								  tr
 								    td Property
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								    td.
-												(docs) Template Syntax

											
										
										
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+								      Element&nbsp;Property<br>
 								      Component&nbsp;Property<br>
 								      Directive&nbsp;property
 								    td
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								      +makeExample('template-syntax/ts/app/app.component.html', 'property-binding-syntax-1')(format=".")
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  tr
 								    td Event
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								    td.
-												(docs) Template Syntax

											
										
										
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+								      Element&nbsp;Event<br>
 								      Component&nbsp;Event<br>
 								      Directive&nbsp;Event
 								    td
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								      +makeExample('template-syntax/ts/app/app.component.html', 'event-binding-syntax-1')(format=".")
-												(docs) Template Syntax

											
										
										
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+								  tr
 								    td Two-way
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								    td.
-												(docs) Template Syntax

											
										
										
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+								      Directive&nbsp;Event
 								      Property
 								    td
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								      +makeExample('template-syntax/ts/app/app.component.html', '2-way-binding-syntax-1')(format=".")
-												(docs) Template Syntax

											
										
										
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+								  tr
 								    td Attribute
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								    td.
-												(docs) Template Syntax

											
										
										
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+								      Attribute
 								      (the&nbsp;exception)
 								    td
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								      +makeExample('template-syntax/ts/app/app.component.html', 'attribute-binding-syntax-1')(format=".")
-												(docs) Template Syntax

											
										
										
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+								  tr
 								    td Class
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								    td.
-												(docs) Template Syntax

											
										
										
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+								      <code>class</code> Property
 								    td
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								      +makeExample('template-syntax/ts/app/app.component.html', 'class-binding-syntax-1')(format=".")
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  tr
 								    td Style
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								    td.
-												(docs) Template Syntax

											
										
										
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+								      <code>style</code> Property
 								    td
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								      +makeExample('template-syntax/ts/app/app.component.html', 'style-binding-syntax-1')(format=".")
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								</div>
 								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  Let’s descend from the architectural clouds and look at each of these binding types in concrete detail.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
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+								.l-main-section
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
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+								  ## Property Binding
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  We write a template **Property Binding** when we want to set a property of a view element to the value of
 								  a [template expression](#template-expressions).
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
 								  The most common Property Binding sets an element property to a component property value as when
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  we bind the source property of an image element to the component’s `heroImageUrl` property.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-1')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  … or disable a button when the component says that it `isUnchanged`.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-2')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  … or set a property of a directive
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-3')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  … or set the model property of a custom component (a great way
 								  for parent and child components to communicate)
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-4')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  ### One-way *in*
 								  People often describe property binding as *one way data binding* because it flows a value in one direction,
 								  from a component’s data property into a target element property.
 								  We cannot use property binding to pull values *out* of the target element.
 								  We can't bind to a property of the target element to read it. We can only set it.
 								.l-sub-section
 								  :marked
 								    Nor can we use property binding to *call* a method on the target element.
 								    If the element raises events we can listen to them with an [event binding](#event-binding).
 								    If we must read a target element property or call one of its methods,
 								    we'll need a different technique.
 								    See the API reference for
 								    [viewChild](../api/core/ViewChild-var.html) and
 								    [contentChild](../api/core/ContentChild-var.html).
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ### Binding Target
 								  A name between enclosing square brackets identifies the target property. The target property in this example is the image element’s `src` property.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-1')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  Some developers prefer the `bind-` prefix alternative, known as the “canonical form”:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-5')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  The target name is always the name of a property, even when it appears to be the name of something else. We see `src` and may think it’s the name of an attribute. No. It’s the name of an image element property.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
 								  Element properties may be the more common targets,
 								  but Angular looks first to see if the name is a property of a known directive
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  as it is in the following example:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-3')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								.l-sub-section
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  :marked
 								    Technically, Angular is matching the name to a directive [input](#inputs-outputs),
 								    one of the property names listed in the directive’s `inputs` array or a property decorated with `@Input()`.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								    Such inputs map to the directive’s own properties.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  If the name fails to match a property of a known directive or element, Angular reports an “unknown directive” error.
 								  ### Property Binding template expressions
 								  Evaluation of the expression should have no visible side-effects. The expression language itself does its part to keep us safe. We can’t assign a value to anything in a Property Binding expression nor use the increment and decorator operators.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  Of course, our expression might invoke a property or method that has side-effects. Angular has no way of knowing that or stopping us.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
 								  The expression could call something like `getFoo()`. Only we know what `getFoo()` does.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  If `getFoo()`  changes something and we happen to be binding to that something, we risk an unpleasant experience. Angular may or may not display the changed value. Angular may detect the change and throw a warning error. Our general advice: stick to data properties and methods that return values and do no more.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  The template expression should evaluate to a value of the type expected by the target property. Most native element properties do expect a string. The image `src` should be set to a string, an URL for the resource providing the image. On the other hand, the `disabled` property of a button expects a Boolean value so our expression should evaluate to `true` or `false`.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  The `hero` property of the `HeroDetail` component expects a `Hero` object which is exactly what we’re sending in the Property Binding:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-4')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  This is good news for the Angular developer.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  If `hero` were an attribute we could not set it to a `Hero` object.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-6')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  We can't set an attribute to an object. We can only set it to a string.
 								  Internally, the attribute may be able to convert that string to an object before setting the like-named element property.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  That’s good to know but not helpful to us when we're trying to pass a significant data object
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  from one component element to another.
 								  The power of Property Binding is its ability to bypass the attribute and
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  set the element property directly with a value of the appropriate type.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ### Property Binding or Interpolation?
 								  We often have a choice between Interpolation and Property Binding. The following binding pairs do the same thing
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'property-binding-vs-interpolation')(format=".")
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
 								  Interpolation is actually a convenient alternative for Property Binding in many cases.
 								  In fact, Angular  translates those Interpolations into the corresponding Property Bindings
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  before rendering the view.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
 								  There is no technical reason to prefer one form to the other.
 								  We lean toward readability which tends to favor interpolation.
 								  We suggest establishing coding style rules for the organization and choosing the form that
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  both conforms to the rules and feels most natural for the task at hand.
-												(docs) Move ToH-pt2 to Jade and break toh-pt1 out of the tutorial index

											
										
										
											2015-10-15 03:51:24 -04:00
+								.l-main-section
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
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+								  <a id="other-bindings"></a>
 								  ## Attribute, Class, and Style Bindings
 								  The template syntax provides specialized one-way bindings for scenarios less well suited to Property Binding.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ### Attribute Binding
 								  We can set the value of an attribute directly with an **Attribute Binding**.
 								.l-sub-section
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The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  :marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								    This is the only exception to the rule that a binding sets a target property. This is the only binding that creates and sets an attribute.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  We have stressed throughout this chapter that setting an element property with a Property Binding is always preferred to setting the attribute with a string. Why does Angular offer Attribute Binding?
-												chore(jade): upgrade to use `marked` filter

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the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
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+								  **We must use Attribute Binding when there is no element property to bind.**
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
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+								  Consider the [aria](https://developer.mozilla.org/en-US/docs/Web/Accessibility/ARIA),
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  [svg](https://developer.mozilla.org/en-US/docs/Web/SVG), and
 								  table span attributes. They are pure attributes.
 								  They do not correspond to element properties and they do not set element properties.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  There are no property targets to bind to.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  We become painfull aware of this fact when we try to write something like this:
 								code-example(language="html").
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
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+								  &lt;tr>&lt;td colspan="{{1 + 1}}">Three-Four&lt;/td>&lt;/tr>
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the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
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+								  … and get the error:
 								code-example(format="", language="html").
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  Template parse errors:
-												(docs) Template Syntax

											
										
										
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+								  Can't bind to 'colspan' since it isn't a known native property
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
 								  As the message says, the `<td>` element does not have a `colspan` property.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  It has the "colspan" *attribute* but
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  interpolation and property binding can only set properties, not attributes.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  We need an Attribute Binding to create and bind to such attributes.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
 								  Attribute Binding syntax resembles Property Binding.
 								  Instead of an element property between brackets, we start with the keyword **`attr`**
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  followed by the name of the attribute and then set it with an expression that resolves to a string.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  Here we bind `[attr.colspan]` to a calulated value:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'attrib-binding-colspan')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  Here's how the table renders:
 								  <table border="1px">
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								    <tr><td colspan="2">One-Two</td></tr>
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
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+								    <tr><td>Five</td><td>Six</td></tr>
-												(docs) Template Syntax

											
										
										
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+								   </table>
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  One of the primary use cases for the Attribute Binding
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  is to set aria attributes as we see in this example
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'attrib-binding-aria')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
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+								  ### Class Binding
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  We can add and remove CSS class names from an element’s `class` attribute with the **Class Binding**.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  Class Binding syntax resembles Property Binding.
 								  Instead of an element property between brackets, we start with the keyword `class` followed
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  by the name of a CSS class: `[class.class-name]`.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  In the following examples we see how to add and remove the application's "special" class
 								  with class bindings.  We start by setting the attribute without binding:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'class-binding-1')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								  We replace that with a binding to a string of the desired class names; this is an all-or-nothing, replacement binding.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'class-binding-2')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								  Finally, we bind to a specific class name.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  Angular adds the class when the template expression evaluates to something truthy and
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  removes the class name when the expression is falsey.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'class-binding-3')(format=".")
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								.l-sub-section
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  :marked
 								    While this is a fine way to toggle a single class name,
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								    we generally prefer the [NgClass directive](#ngClass) for managing multiple class names at the same time.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ### Style Binding
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  We can set inline styles with a **Style Binding**.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  Style Binding syntax resembles Property Binding.
 								  Instead of an element property between brackets, we start with the key word `style`
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  followed by the name of a CSS style property: `[style.style-property]`.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'style-binding-1')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								  Some Style Binding styles have unit extension. Here we conditionally set the `fontSize` in  “em” and “%” units .
 								+makeExample('template-syntax/ts/app/app.component.html', 'style-binding-2')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								.l-sub-section
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  :marked
 								    While this is a fine way to set a single style,
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								    we generally prefer the [NgStyle directive](#ngStyle) when setting several inline styles at the same time.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
 								.l-main-section
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
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+								  ## Event Binding
 								  The bindings we’ve met so far flow data in one direction *from the component to an element*.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  Users don’t just stare at the screen. They enter text into a input box. They pick items from a list.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  They click buttons. Such user actions may result in a flow of data in the opposite direction,
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ***from an element to the component***.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
 								  The only way to know about a user action is to listen for certain events such as
 								  keystrokes, mouse movements, clicks and touches.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  We declare our interest in user actions through Angular Event Binding.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  Event Binding syntax consists of a target event within parentheses on the left of an equal sign and a quoted
 								  [**template statement**](#template-statements) on the right.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  The following Event Binding listens for the button’s click event and calls the component's `onSave()` method:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'event-binding-1')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ### Binding target
 								  A **name between enclosing parentheses** identifies the target event. In the following example, the target is the button’s click event.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'event-binding-1')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  Some developers prefer the `on-` prefix alternative, known as the “canonical form”:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'event-binding-2')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  Element events may be the more common targets, but Angular looks first to see if the name matches an event property
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  of a known directive as it does in the following example:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'event-binding-3')(format=".")
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  If the name fails to match an element event or an output property of a known directive,
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  Angular reports an “unknown directive” error.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  ### $event and event handling statements
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  In an Event Binding, Angular sets up an event handler for the target event.
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  When the event is raised, the handler executes the template statement.
 								  The template statement typically involves a receiver that wants to do something
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  in response to the event such as take a value from the HTML control and store it
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  in a model.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  The binding conveys information about the event including data values through
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  an **event object named `$event`**.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  The shape of the $event object is determined by the target event itself.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  If the target event is a native DOM element event, the `$event` is a
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  [DOM event object]( https://developer.mozilla.org/en-US/docs/Web/Events) with properties such as `target` and `target.value`.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  Consider this example:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'without-NgModel')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  We’re binding the input box `value` to a `firstName` property and we’re listening for changes by binding to the input box’s `input` event.
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  When the user makes changes, the `input` event is raised, and the binding executes the statement within a context that includes the DOM event object, `$event`.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  We must follow the `$event.target.value` path to get the changed text so we can update the `firstName`
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  If the event belongs to a directive (remember: components are directives), `$event` has whatever shape the directive chose to produce.
 								  Consider a `HeroDetailComponent` that produces `deleted` events with an `EventEmitter`.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/hero-detail.component.ts', 'deleted', 'HeroDetailComponent.ts (excerpt)')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  When something invokes the `onDeleted()` method, we "emit" a `Hero` object.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  Now imagine a parent component that listens for that event with an Event Binding.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'event-binding-to-component')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  The event binding surfaces the *hero-to-delete* emitted by `HeroDetail` to the statement via the `$event` variable.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  We pass it along to the parent `onHeroDeleted()` method.
 								  That method presumably knows how to delete the hero.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  Evaluation of this Event Binding template statement has a side-effect. It deletes a hero.
 								  Side-effects are not just OK; they are expected.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  The statement could update the model thereby triggering other changes that percolate through the system, changes that
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  are ultimately displayed in this view and other views.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  The event processing may result in queries and saves to a remote server. It's all good.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ### Event bubbling and propagation
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  Angular invokes the event-handling statement if the event is raised by the current element or one of its child elements.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'event-binding-bubbling')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  Many DOM events, both [native](https://developer.mozilla.org/en-US/docs/Web/Guide/Events/Overview_of_Events_and_Handlers ) and [custom](https://developer.mozilla.org/en-US/docs/Web/Guide/Events/Creating_and_triggering_events ),  “bubble” events up their ancestor tree of DOM elements until an event handler along the way prevents further propagation.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								.l-sub-section
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  :marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								    `EventEmitter` events don’t bubble.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  The result of an Event Binding statement determines if
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  [event propagation](https://developer.mozilla.org/en-US/docs/Web/API/Document_Object_Model/Examples#Example_5:_Event_Propagation)
 								  continues or stops with the current element.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  Event propagation stops if the binding statement returns a falsey value (as does a method with no return value).
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  Clicking the button in this next example triggers a save;
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  the click doesn't make it to the outer `<div>` so it's save is not called:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'event-binding-no-propagation')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  Propagation continues if the statement returns a truthy value. The click is heard both by the button
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  and the outer `<div>`, causing a double save:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'event-binding-propagation')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								.l-main-section
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								  <a name="ngModel"></a>
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ## Two-Way Binding with NgModel
 								  When developing data entry forms we often want to both display a data property and update that property when the user makes changes.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  The `NgModel` directive serves that purpose as seen in this example:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'NgModel-1')(format=".")
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								.callout.is-important
 								  header
 								    :marked
 								       <span style="font-family:consolas; monospace">[()]</span> = banana in a box
 								  :marked
 								    To remember that the parentheses go inside the brackets, visualize a *banana in a box*.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  If we prefer the “canonical” prefix form to the punctuation form, we can write
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'NgModel-2')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  There’s a story behind this construction, a story that builds on the Property and Event Binding techniques we learned previously.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  We could have achieved the same result as `NgModel` with separate bindings to the
 								  the `<input>` element's  `value` property and `input` event.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'without-NgModel')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								  That’s cumbersome. Who can remember what element property to set and what event reports user changes?
 								  How do we extract the currently displayed text from the input box so we can update the data property?
 								  Who wants to look that up each time?
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								  That `ngModel` directive hides these onerous details. It wraps the element’s `value` property, listens to the `input` event,
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  and raises its own event with the changed text ready for us to consume.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'NgModel-3')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								  That’s an improvement. It should be better.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  We shouldn't have to mention the data property twice. Angular should be able to read the component’s data property and set it
-												chore(typo): fix a typo about [{}] reported in feedback

											
										
										
											2015-12-16 17:10:27 -05:00
+								  with a single declaration &mdash; which it can with the `[( )]` syntax:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'NgModel-1')(format=".")
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								.l-sub-section
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  :marked
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								    Internally, Angular maps the term, `ngModel`, to an `ngModel` input property and an
 								    `ngModelChange` output property.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								    That’s a specific example of a more general pattern in which it matches `[(x)]` to an `x` input property
-												docs(guides): Fix typos "-change" -> "Change"
closes #605

											
										
										
											2015-12-25 05:45:08 -05:00
+								    for Property Binding and an `xChange` output property for Event Binding.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								    We can write our own two-way binding directive that follows this pattern if we're ever in the mood to do so.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  Is `[(ngModel)]` all we need? Is there ever a reason to fall back to its expanded form?
 								  Well `NgModel` can only set the target property.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  What if we need to do something more or something different when the user changes the value?
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  Let's try something silly like forcing the input value to uppercase.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'NgModel-4')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								  Here are all variations in action, including the uppercase version:
 								figure.image-display
-												docs(Template Syntax): correct minor oversights in a.53 update
closes #494

											
										
										
											2015-12-14 01:29:37 -05:00
+								    img(src='/resources/images/devguide/template-syntax/ng-model-anim.gif' alt="NgModel variations")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
 								.l-main-section
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  <a name="directives"></a>
 								  ## Built-in Directives
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  Earlier versions of Angular included over seventy built-in directives.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  The community contributed many more and individuals have created countless private directives for internal applications.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
 								  We don’t need many of those directives in Angular 2.
 								  Quite often we can achieve the same results with the more capable and expressive Angular 2 binding system.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  Why create a directive to handle a click when we can write a simple binding such as this?
-												docs(Template Syntax): correct minor oversights in a.53 update
closes #494

											
										
										
											2015-12-14 01:29:37 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'event-binding-1')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  We still benefit from directives that simplify complex tasks.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  Angular still ships with built-in directives; just not as many.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  We will write our own directives; just not as many.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): fix typos in template-syntax.jade
closes #609

											
										
										
											2015-12-27 04:38:16 -05:00
+								  In this segment we review some of the most frequently used built-in directives.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								<a id="ngClass"></a>
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								.l-main-section
 								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ### NgClass
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
 								  We typically control how elements appear
 								  by adding and removing CSS classes dynamically.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  We can bind to `NgClass` to add or remove several classes simultaneously.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  We prefer to use a [Class Binding](#class-binding) to add or remove a *single* class.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'class-binding-3a')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  The `NgClass` directive may be the better choice
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  when we want to add or remove *many* classes at the same time.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
 								  Our favorite way to apply `NgClass` is by binding it to a key:value control object. Each key of the object is a class name and its value is `true` if the class should be added, `false` if it should be removed.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  Consider a component method such as `setClasses` that returns its approval of two class names:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.ts', 'setClasses')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								  Now add an `NgClass` property binding to call it like this
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'NgClass-1')(format=".")
-												(docs) template-syntax - fix - ng-switch should be <h3>
closes #404

											
										
										
											2015-11-24 16:07:08 -05:00
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								<a id="ngStyle"></a>
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								.l-main-section
 								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ### NgStyle
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  We may set inline styles dynamically based on the state of the component.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  We bind to `NgStyle` to set many inline styles simultaneously.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  We prefer to use a [Style Binding](#style-binding) to set a *single* style value.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'NgStyle-1')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  The `NgStyle` directive may be the better choice
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  when we want to set *many* inline styles at the same time.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  We apply `NgStyle` by binding it to a key:value control object.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  Each key of the object is a style name and its value is whatever is appropriate for that style.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  Consider a component method such as `setStyles` that returns an object defining three styles:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.ts', 'setStyles')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								  Now add an `NgStyle` property binding to call it like this
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'NgStyle-2')(format=".")
-												docs(Template Syntax): correct minor oversights in a.53 update
closes #494

											
										
										
											2015-12-14 01:29:37 -05:00
+								:marked
 								  Alternatively, we can return an object with camelCase style property names with the same effects:
 								+makeExample('template-syntax/ts/app/app.component.ts', 'setStyles2')(format=".")
 								:marked
-												(docs) template-syntax - fix - ng-switch should be <h3>
closes #404

											
										
										
											2015-11-24 16:07:08 -05:00
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								<a id="ngIf"></a>
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								.l-main-section
 								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ### NgIf
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  We can add an element sub-tree (an element and its children) to the DOM  by binding an `NgIf` directive to a truthy expression.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'NgIf-1')(format=".")
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								.alert.is-critical
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  :marked
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								    The leading asterisk (\*) in front of `ngIf` is a critical part of this syntax.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								    See the section below on [\* and &lt;template>](#star-template).
 								:marked
 								  Binding to a falsey expression removes the element sub-tree from the DOM.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'NgIf-2')(format=".")
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  #### Visibility and NgIf are not the same
 								  We can show and hide an element sub-tree (the element and its children) with a  [Class](#class-binding) or a [Style](#style-binding) binding:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'NgIf-3')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  Hiding a sub-tree is quite different from excluding a sub-tree with `NgIf`.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  When we hide the element sub-tree, it remains in the DOM.
 								  Components in the sub-tree are preserved along with their state.
 								  Angular may continue to check for changes even to invisible properties.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  The sub-tree may tie up substantial memory and computing resources.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  When `NgIf` is `false`, Angular physically removes the element sub-tree from the DOM.
 								  It destroys components in the sub-tree along with their state which may free up substantial resources
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  resulting in better performance for the user.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  The show/hide technique is probably fine for small element trees.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  We should be wary when hiding large trees; `NgIf` may be the safer choice. Always measure before leaping to conclusions.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								<a id="ngSwitch"></a>
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								.l-main-section
 								:marked
-												(docs) template-syntax - fix - ng-switch should be <h3>
closes #404

											
										
										
											2015-11-24 16:07:08 -05:00
+								  ### NgSwitch
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  We bind to `NgSwitch` when we want to display *one* element tree (an element and its children)
-												docs(template syntax): fix "elment" typo
closes #649

											
										
										
											2016-01-05 05:01:35 -05:00
+								  from a *set* of possible element trees based on some condition.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  Angular only puts the *selected* element tree into the DOM.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  Here’s an example:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'NgSwitch')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												docs(router): new chapter
Ward and Jeremy
Todo: EXCLUDE Old router doc for reference while re-writing

											
										
										
											2015-12-10 12:40:54 -05:00
+								  We bind the parent `NgSwitch` directive to an expression returning a “switch value”.  The value is a string in this example but it can be a value of any type.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(router): new chapter
Ward and Jeremy
Todo: EXCLUDE Old router doc for reference while re-writing

											
										
										
											2015-12-10 12:40:54 -05:00
+								  The parent `NgSwitch` directive controls a set of child`<template>` elements. Each `<template>` wraps a candidate subtree. A template is either pegged to a “match value” expression or marked as the default template.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  **At any particular moment, only one of these templates will be rendered**
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  If the template’s “match value” equals the “switch value”, Angular adds the template’s sub-tree to the DOM. If no template is a match and there is a default template, Angular adds the default template’s sub-tree to the DOM. Angular removes and destroys the sub-tree’s of all other templates.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(router): new chapter
Ward and Jeremy
Todo: EXCLUDE Old router doc for reference while re-writing

											
										
										
											2015-12-10 12:40:54 -05:00
+								  There are three collaborating directives at work here.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+. `ngSwitch` - bound to an expression that returns the switch value.
 . `ngSwitchWhen` - bound to an expression returning a match value.
 . `ngSwitchDefault` - a marker attribute on the default template.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								<a id="ngFor"></a>
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								.l-main-section
 								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ### NgFor
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  `NgFor` is a “repeater” directive. It will be familiar if we’ve written repeaters for other view engines.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  Our goal is to present a list of items. We define a block of HTML that defines how a single item should be displayed.
 								  We tell Angular to use that block as a template for rendering each item in the list.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  Here is an example of `NgFor` applied to a simple `<div>`.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'NgFor-1')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								  We can apply an `NgFor` to a component element as well as we do in this example:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'NgFor-2')(format=".")
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								.alert.is-critical
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  :marked
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								    The leading asterisk (\*) in front of `ngFor` is a critical part of this syntax.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								    See the section below on [\* and &lt;template>](#star-template).
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								  The text assigned to `*ngFor` is the instruction that guides the repeater process.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								.l-sub-section
 								  :marked
 								    #### NgFor Micro-syntax
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								    The string assigned to `*ngFor` is not a [template expression](#template-expressions).
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								    It’s a little language of its own called a “micro-syntax” that Angular interprets. In this example it means:
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								    >*Take each hero in the `heroes` array, store it in the local `hero` variable, and make it available to the templated HTML
 								    for each iteration*.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								    Angular translates this instruction into a new set of elements and bindings.
 								    We’ll talk about this in the next section about templates.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  In our two examples, the `ngFor` directive iterates over the `heroes` array returned by the parent component’s `heroes` property
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  and stamps out instances of the element to which it is applied.
 								  Angular creates a fresh instance of the template for each hero in the array.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  The (#) character before "hero" identifies a [local template variable](#local-vars) called `hero`.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  We reference this variable within the template to access a hero’s properties as we’re doing in the interpolation
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  or we can pass it in a binding to a component element as we're doing with `hero-detail`.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  #### NgFor with index
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  The `ngFor` directive supports an optional index that increases from 0 to the length of the array for each iteration.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  We can capture that in another local template variable (`i`) and use it in our  template too.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  This next example stamps out rows that display like "1 - Hercules Son of Zeus":
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'NgFor-3')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								.l-sub-section
 								  :marked
 								    Learn about other special values such as `last`, `even` and `odd` in the [API](../api/common/NgFor-directive.html) guide.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								<a name="star-template"></a>
 								<a name="structural-directive"></a>
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								.l-main-section
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ## * and &lt;template>
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								  When we reviewed the `ngFor` and `ngIf` built-in directives we called out an oddity of the syntax, the asterisk (*)  that appears before the directive name.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  This is a bit of “**syntactic sugar**” that makes it easier to read and write directives that modify HTML layout
 								  with the help of templates.
 								  `NgFor`, `NgIf`, and `NgSwitch` all add and remove element subtrees that are wrapped in `<template>` tags.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								  With the [NgSwitch](#ngSwitch) directive we always write the `<template>` tags explicitly as we saw [above](#ngSwitch).
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  There isn’t much choice; we define a different template for each switch choice
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  and let the directive render the template that matches the switch value.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								  [NgFor](#ngFor) and [NgIf](#ngIf) only need one template,
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  the *template-to-repeat* and the *template-to-include* respectively.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  The (\*) prefix syntax is a convenient way for developers to skip the `<template>` wrapper tags and
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  focus directly on the HTML element to repeat or include.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  Angular sees the (*) and expands the HTML into the `<template>` tags for us.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								  ### Expanding `*ngIf`
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  We can do that ourselves if we wish. Instead of writing ...
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'Template-1')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  … we can write:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'Template-2')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								  Notice the (\*) is gone and we have a [Property Binding](#property-binding) to the `ngIf`
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  directive, applied in this case to the `<template>` rather than
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  the application’s `hero-detail` component.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  The `[hero]="currentHero"` binding remains on the child `<hero-detail>`
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  element inside the template. Angular does that too.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								.callout.is-critical
 								  header Remember the brackets!
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  :marked
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								    Don’t make the mistake of writing `ngIf="currentHero"`!
 								    That syntax assigns the *string* value, "currentHero", to `ngIf`.
 								    In JavaScript a non-empty string is a truthy value so `ngIf` would always be
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								    `true` and Angular will always display the `hero-detail`
 								    … even when there is no `currentHero`!
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
 								:marked
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								  ### Expanding `*ngFor`
 								  A similar transformation applies to `*ngFor`. We can "de-sugar" the syntax ourselves and go from ...
 								+makeExample('template-syntax/ts/app/app.component.html', 'NgFor-2')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ... to
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'Template-3')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								  ... and from there to
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'Template-4')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								  This is a bit more complex than `NgIf` because a repeater has more moving parts to configure.
 								  In this case, we have to remember the `NgForOf` directive that identifies the list.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								  It should be clear why we prefer the `*ngFor` syntax to writing out this expanded HTML ourselves.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								<a id="local-vars"></a>
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								.l-main-section
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ## Local template variables
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  A **local template variable** is a vehicle for moving data across element lines.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
 								  We've seen the `#hero` local template variable several times in this chapter,
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								  most prominently when writing [NgFor](#ngFor) repeaters.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  In the [* and &lt;templates>](#star-template) segment we learned how Angular expands
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								  an `*ngFor` on a component tag into a `<template>` that wraps the component.
 								+makeExample('template-syntax/ts/app/app.component.html', 'Template-4')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								  The (#) prefix character in front of "hero" means that we're defining a `hero` variable.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								.l-sub-section
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  :marked
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								    Some folks don't like the (#) character.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								    The `var-` prefix is the  “cannonical” alternative to "#". We could have declared our variable as `var-hero`.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  We defined `hero` on the outer `<template>` element where it becomes the current hero item
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  as Angular iterates through the list of heroes.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  The `hero` variable appears again in the binding on the inner `<hero-detail>` component element.
 								  That's how each instance of the `<hero-detail>` gets its hero.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  ### Referencing a local template variable
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  We can reference a local template variable on the same element, on a sibling element, or on
 								  any of its child elements.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  Here are two other examples of creating and consuming a local template variable:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'var-phone')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								  ### How it gets its value
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  The value assigned to the variable depends upon the context.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  When a directive is present on the element, as it is in the earlier NgFor `<hero-detail>` component example,
 								  the directive sets the value.  Accordingly, the `NgFor` directive
-												docs(template-syntax): fix typos in template-syntax.jade
closes #609

											
										
										
											2015-12-27 04:38:16 -05:00
+								  sets the `hero` variable to a hero item from the `heroes` array.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  When there is no directive present, as in phone and fax examples,
 								  Angular sets the variable to the element on which it was defined.
 								  We defined these variables on the `input` elements.
 								  We’re passing those `input` element objects across to the
 								  button elements where they become arguments to the `call()` methods in the event bindings.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(Template Syntax): correct minor oversights in a.53 update
closes #494

											
										
										
											2015-12-14 01:29:37 -05:00
+								  ### NgForm and local template variables
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  Let's look at one final example, a Form, the poster child for local template variables.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  The HTML for a form can be quite involved as we saw in the [Forms](forms.html) chapter.
 								  The following is a *simplified* example &mdash; and it's not simple at all.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'var-form')
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								  A local template variable, `theForm`, appears three times in this example, separated
 								  by a large amount of HTML.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'var-form-a')
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								  What is the value of `theForm`?
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
 								  It would be the [HTMLFormElement](https://developer.mozilla.org/en-US/docs/Web/API/HTMLFormElement)
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  if Angular hadn't taken it over.
-												docs(Template Syntax): correct minor oversights in a.53 update
closes #494

											
										
										
											2015-12-14 01:29:37 -05:00
+								  It's actually `ngForm`, a reference to the Angular built-in `NgForm` directive that wraps the native `HTMLFormElement`
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  and endows it with additional super powers such as the ability to
 								  track the validity of user input.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  This explains how we can disable the submit button by checking `theForm.form.valid`
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  and pass an object with rich information to the parent component's `onSubmit` method.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								<a id="inputs-outputs"></a>
 								.l-main-section
 								:marked
 								  ## Input and Output Properties
 								  We can only bind to **target directive** properties that are either **inputs** or **outputs**.
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
 								.alert.is-important
 								  :marked
 								    A *component is a directive*. We use the terms "directive" and "component" interchangeably.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								.l-sub-section
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  :marked
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								    We're drawing a sharp distinction between a data binding **target** and a data binding **source**.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								    The *target* of a binding is to the *left* of the (=).
 								    The *source* is on the *right* of the (=).
 								    The *target* of a binding is the property or event inside the binding punctuation: `[]`, `()` or `[()]`.
 								    The *source* is either inside quotes (") or within an interpolation (`{}`).
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								    Every member of a **source** directive or component is automatically available for binding.
 								    We don't have to do anything special to access a component member in a template expression or statement.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								    We have *limited* access to members of a **target** directive or component.
 								    We can only bind to properties that are explicitly identified as *inputs* and *outputs*.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  In this chapter we’ve focused mainly on binding to component members within template expressions and statements
 								  that appear on the *right side of the binding declaration*.
 								  A member in that position is a binding “data source”.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  In the following example, `iconUrl` and `onSave` are members of the `AppComponent`
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  referenced within quoted syntax to the right of the (=).
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'io-1')(format=".")
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  They are *neither inputs nor outputs* of `AppComponent`. They are data sources for their bindings.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  Now look at the `HeroDetailComponent` when it is the **target of a binding**.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'io-2')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  Both `HeroDetail.hero` and `HeroDetail.deleted` are on the **left side** of binding declarations.
 								  `HeroDetail.hero` is inside brackets; it is the target of a Property Binding.
 								  `HeroDetail.deleted` is inside parentheses; it is the target of an Event Binding.
 								  ### Declaring input and output properties
 								  Target properties must be explicitly marked as inputs or outputs.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  When we peek inside `HeroDetailComponent` we see that these properties are marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  with decorators as input and output properties.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/hero-detail.component.ts', 'input-output-1')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								.l-sub-section
 								  :marked
 								    Alternatively, we can identify them in the `inputs` and `outputs` arrays
 								    of the directive metadata as seen in this example:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								  +makeExample('template-syntax/ts/app/hero-detail.component.ts', 'input-output-2')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  <br>
 								  :marked
-												docs(Template Syntax): correct minor oversights in a.53 update
closes #494

											
										
										
											2015-12-14 01:29:37 -05:00
+								    We can specify an input/output property with a decorator or in one the metadata arrays.
 								    Don't do both!
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  ### Input or Output?
 								  *Input* properties usually receive data values.
 								  *Output* properties expose event producers (e.g, an `EventEmitter`).
 								  The terms "input" and "output" reflect the perspective of the target directive.
 								  `HeroDetail.hero` is an ***input*** property from the perspective of `HeroDetailComponent`
 								  because data flow  *into* that property from a template binding expression.
 								  `HeroDetail.deleted` is an ***output*** property from the perspective of `HeroDetailComponent`
 								  because events stream *out* of that property and toward the handler in a template binding statement.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  ### Aliasing input/output properties
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  Sometimes we want the public name of an input/output property to be different from the internal name.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  This is frequently the case with [Attribute Directives](attribute-directives.html).
 								  Directive consumers expect to bind to the name of the directive.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  For example, we expect to bind to the `myClick` event property of the `MyClickDirective`.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  The directive name is often a poor choice for the the internal property name
 								  because it rarely describes what the property does.
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  `myClick` is not a good name for a property that emits click events.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								  Fortunately, we can have a public name for the property that meets conventional expectations
 								  and use a different name internally
 								  by providing a public alias for the internal property name in the decorator like this:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/my-click.directive.ts', 'my-click-output-1')(format=".")
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								:marked
 								  Now the directive name, `myClick`, is the public facing property name to which we can bind
 								+makeExample('template-syntax/ts/app/app.component.html', 'my-click')(format=".")
 								:marked
 								  while inside the directive, the property is known as `clicks`.
 								  With aliasing we please both the directive consumer and the directive author.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								.l-sub-section
 								  :marked
-												docs(template-syntax): sample/devmode fix + text updates
closes #692

											
										
										
											2016-01-10 20:07:19 -05:00
+								    We can alias property names in the `inputs` and `outputs` arrays as well.
 								    We write a colon-delimited string with
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								    the internal property name on the left and the public name on the right:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								  +makeExample('template-syntax/ts/app/my-click.directive.ts', 'my-click-output-2')(format=".")
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								<a id="expression-operators"></a>
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								.l-main-section
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ## Template Expression Operators
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  The template expression language employs a subset of JavaScript syntax supplemented with some special operators
-												(docs) tutorial index fixes

											
										
										
											2015-11-01 00:13:18 -04:00
+								  for specific scenarios. We'll cover two of them, "pipe" and "Elvis".
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  <a id="pipe"></a>
 								  ### The Pipe Operator ( | )
 								  The result of an expression may require some transformation before we’re ready to use it in a binding.  For example, we may wish to display a number as a currency, force text to uppercase, or filter a list and sort it.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
 								  Angular [Pipes](./pipes.html) are a good choice for small transformations such as these.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  Pipes are simple functions that accept an input value and return a transformed value.
 								  They are easy to apply within template expressions using the **pipe operator ( | )**:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'pipes-1')(format=".")
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  The pipe operator passes the result of an expression on the left to a pipe function on the right.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  We can chain expressions through multiple pipes
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'pipes-2')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								  And we can configure them too:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'pipes-3')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								  The `json` pipe is particular helpful for debugging our bindings:
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'pipes-json')(format=".")
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  <a id="elvis"></a>
 								  ### The Elvis Operator ( ?. ) and null property paths
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  The Angular **“Elvis” operator ( ?. )** is a fluent and convenient way to guard against null and undefined values in property paths.
 								  Here it is, protecting against a view render failure if the `currentHero` is null.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'elvis-2')(format=".")
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  Let’s elaborate on the problem and this particular solution.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  What happens when the following data bound `title` property is null?
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'elvis-1')(format=".")
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  The view still renders but the displayed value is blank; we see only "`The title is`" with nothing after it.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  That is reasonable behavior. At least the app doesn't crash.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  Suppose the template expression involves a property path as in this next example
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  where we’re displaying the `firstName` of a null hero.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								code-example(format="" language="html").
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  The null hero's name is {{nullHero.firstName}}
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  JavaScript throws a null reference error and so does Angular:
 								code-example(format="" language="html").
 								  TypeError: Cannot read property 'firstName' of null in [null]
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  Worse, the *entire view disappears*.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  We could claim that this is reasonable behavior if we believed that the `hero` property must never be null.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  If it must never be null and yet it is null,
 								  we've made a programming error that should be caught and fixed.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  Throwing an exception is the right thing to do.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
 								  On the other hand, null values in the property path may be OK from time to time,
 								  especially when we know the data will arrive eventually.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  While we wait for data, the view should render without complaint and
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  the null property path should display as blank just as the `title` property does.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  Unfortunately, our app crashes when the `currentHero` is null.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								  We could code around that problem with [NgIf](#ngIf)
 								+makeExample('template-syntax/ts/app/app.component.html', 'elvis-4')(format=".")
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  Or we could try to chain parts of the property path with `&&`, knowing that the expression bails out
 								  when it encounters the first null.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'elvis-5')(format=".")
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								:marked
 								  These approaches have merit but they can be cumbersome, especially if the property path is long.
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  Imagine guarding against a null somewhere in a long property path such as `a.b.c.d`.
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  The Angular  **“Elvis” operator ( ?. )** is a more fluent and convenient way to guard against nulls in property paths.
-												fix(template syntax): minor fixes
closes #535

											
										
										
											2015-12-15 17:10:10 -05:00
+								  The expression bails out when it hits the first null value.
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  The display is blank but the app keeps rolling and there are no errors.
-												docs(Template Syntax): update to a.53 (kebab work)
closes #493

											
										
										
											2015-12-13 23:10:03 -05:00
+								+makeExample('template-syntax/ts/app/app.component.html', 'elvis-6')(format=".")
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												docs(template-syntax): drive jade from sample
closes #456

											
										
										
											2015-12-07 16:31:26 -05:00
+								  It works perfectly with long property paths too:
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ```
 								  a?.b?.c?.d
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								  ```
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
 								.l-main-section
-												chore(jade): upgrade to use `marked` filter

The `Transformers.markdown` (`:markdown`) filter is deprecated. This commit updates
the entire docs project to use the `jstransformer-marked` (`:marked') filter.

											
										
										
											2015-11-10 13:31:46 -05:00
+								:marked
-												(docs) Template Syntax

											
										
										
											2015-10-16 23:39:30 -04:00
+								  ## What Next?
-												docs: Change label of case to 'kebab' for attrs
closes #399

The docs refer to `this-style-of-casing` as snake case, but it's
actually "kebab case." Snake case looks `like_this_instead`.

https://en.wikipedia.org/wiki/Letter_case#Special_case_styles

											
										
										
											2015-11-21 23:26:28 -05:00
+								  We’ve completed our survey of Template Syntax. Time to put that knowledge to work as we write our own Components and Directives.