include ../_util-fns a(id="top") :marked There are many conceptual and syntactical differences between Angular 1 and Angular 2. This chapter provides a quick reference guide to some of the common Angular 1 syntax and its equivalent in Angular 2. :marked **See the Angular 2 syntax in this [live example](/resources/live-examples/cb-a1-a2-quick-reference/ts/plnkr.html)**. ## Contents This chapter covers * [Template Basics](#template-basics) - binding and local variables * [Template Directives](#template-directives) - built-in directives `ngIf` and `ngClass` * [Filters/Pipes](#filters-pipes) - built-in *filters*, known as *pipes* in Angular 2 * [Controllers/Components](#controllers-components) - *controllers* are *components* in Angular 2. Also covers modules. * [Style Sheets](#style-sheets) - more options for CSS in Angular 2. * [String date pipe](#string-dates) - a tip for displaying string date values. .l-main-section :marked ## Template Basics Templates are the user-facing part of an Angular application and are written in HTML. The following are some of the key Angular 1 template features with the equivalent template syntax in Angular 2. - var top="vertical-align:top" table(width="100%") col(width="50%") col(width="50%") tr th Angular 1 th Angular 2 tr(style=top) td :marked ### Bindings/Interpolation code-example. Your favorite hero is: {{vm.favoriteHero}} :marked In Angular 1, an expression in curly braces denotes one-way binding. This binds the value of the element to a property in the controller associated with this template. When using the `controller as` syntax, the binding is prefixed with the controller alias (`vm`) because we have to be specific about the source of the binding. td :marked ### Bindings/Interpolation +makeExample('cb-a1-a2-quick-reference/ts/app/movie-list.component.html', 'interpolation')(format="." ) :marked In Angular 2, a template expression in curly braces still denotes one-way binding. This binds the value of the element to a property of the component. The context of the binding is implied and is always the associated component, so it needs no reference variable. For more information see [Template Syntax](../guide/template-syntax.html#interpolation). tr(style=top) td :marked ### Filters code-example. <td>{{movie.title | uppercase}}</td> :marked To filter output in our templates in Angular 1, we use the pipe character (|) and one or more filters. In this example, we filter the `title` property to uppercase. td :marked ### Pipes +makeExample('cb-a1-a2-quick-reference/ts/app/app.component.html', 'uppercase')(format="." ) :marked In Angular 2, we use similar syntax with the pipe (|) character to filter output, but now we call them **pipes**. Many (but not all) of the built-in filters from Angular 1 are built-in pipes in Angular 2. See the heading [Filters / Pipes](#Pipes) below for more information. tr(style=top) td :marked ### Local variables code-example(format=""). <tr ng-repeat="movie in vm.movies"> <td>{{movie.title}}</td> </tr> :marked Here, `movie` is a user-defined local variable. td :marked ### Local variables +makeExample('cb-a1-a2-quick-reference/ts/app/app.component.html', 'local')(format="." ) :marked In Angular 2, we have true local template variables that are explicitly defined using the hash (#) symbol. Using a local template variable, we can move data between elements in the template. We can use the local template variable on the same element, on sibling elements, or on any child elements. For more information see [Template Syntax](../guide/template-syntax.html#local-vars). :marked [Back to top](#top) .l-main-section :marked ## Template Directives Angular 1 provides over seventy built-in directives for use in our templates. Many of them are no longer needed in Angular 2 because of its more capable and expressive binding system. The following are some of the key Angular 1 built-in directives and the equivalent feature in Angular 2. table(width="100%") col(width="50%") col(width="50%") tr th Angular 1 th Angular 2 tr(style=top) td :marked ### ng-app code-example. <body ng-app="movieHunter"> :marked The application startup process is called **bootstrapping**. Although we can bootstrap an Angular 1 app in code, many applications bootstrap declaratively with the `ng-app` directive, giving it the name of the application's module (`movieHunter`). td :marked ### Bootstrapping +makeExample('cb-a1-a2-quick-reference/ts/app/main.ts')(format="." ) :marked Angular 2 does not have a bootstrap directive. We always launch the app in code by explicitly calling a bootstrap function and passing it the name of the application's module (`AppComponent`). For more information see [Quick Start](../quickstart.html). tr(style=top) td :marked ### ng-class code-example(format=""). <div ng-class="{active: isActive}"> <div ng-class="{active: isActive, shazam: isImportant}"> :marked In Angular 1, the `ng-class` directive includes/excludes CSS classes based on an expression. That expression is often a key-value control object with each key of the object defined as a CSS class name, and each value defined as a template expression that evaluates to a Boolean value. In the first example, the `active` class is applied to the element if `isActive` is true. We can specify multiple classes as shown in the second example. td :marked ### ngClass +makeExample('cb-a1-a2-quick-reference/ts/app/app.component.html', 'ngClass')(format="." ) :marked In Angular 2, the `ngClass` directive works similarly. It includes/excludes CSS classes based on an expression. In the first example, the `active` class is applied to the element if `isActive` is true. We can specify multiple classes as shown in the second example. Angular 2 also has **class binding**, which is a good way to add or remove a single class as shown in the third example. For more information see [Template Syntax](../guide/template-syntax.html#other-bindings). tr(style=top) td :marked ### ng-click code-example(format=""). <button ng-click="vm.toggleImage()"> <button ng-click="vm.toggleImage($event)"> :marked In Angular 1, the `ng-click` directive allows us to specify custom behavior when an element is clicked. In the first example, when the button is clicked, the `toggleImage()` method in the controller referenced by the `vm` `controller as` alias is executed. The second example demonstrates passing in the `$event` object, which provides details about the event to the controller. td :marked ### bind to the `click` event +makeExample('cb-a1-a2-quick-reference/ts/app/app.component.html', 'event-binding')(format="." ) :marked The Angular 1 event-based directives do not exist in Angular 2. Rather, we define one-way binding from the template view to the component using **event binding**. For event binding, we define the name of the target event within parenthesis and specify a template statement in quotes to the right of the equals. Angular 2 then sets up an event handler for the target event. When the event is raised, the handler executes the template statement. In the first example, when the button is clicked, the `toggleImage()` method in the associated component is executed. The second example demonstrates passing in the `$event` object, which provides details about the event to the component. For a list of DOM events, see: https://developer.mozilla.org/en-US/docs/Web/Events. For more information see [Template Syntax](../guide/template-syntax.html#event-binding). tr(style=top) td :marked ### ng-controller code-example(format=""). <div ng-controller="MovieListCtrl as vm"> :marked In Angular 1, the `ng-controller` directive attaches a controller to the view. Using the `ng-controller` (or defining the controller as part of the routing) ties the view to the controller code associated with that view. td :marked ### Component decorator +makeExample('cb-a1-a2-quick-reference/ts/app/movie-list.component.ts', 'component')(format="." ) :marked In Angular 2, the template no longer specifies its associated controller. Rather, the component specifies its associated template as part of the component class decorator. For more information see [Architecture Overview](../guide/architecture.html#component). tr(style=top) td :marked ### ng-hide In Angular 1, the `ng-hide` directive shows or hides the associated HTML element based on an expression. See [ng-show](#ng-show) for more information. td :marked ### bind to the `hidden` property In Angular 2, we use property binding; there is no built-in *hide* directive. See [ng-show](#ng-show) for more information. tr(style=top) td :marked ### ng-href code-example(format=""). <a ng-href="angularDocsUrl">Angular Docs</a> :marked The `ng-href` directive allows Angular 1 to preprocess the `href` property so it can replace the binding expression with the appropriate URL before the browser fetches from that URL. In Angular 1, the `ng-href` is often used to activate a route as part of navigation. code-example(format=""). <a ng-href="#movies">Movies</a> :marked Routing is handled differently in Angular 2. td :marked ### bind to the `href` property +makeExample('cb-a1-a2-quick-reference/ts/app/app.component.html', 'href')(format="." ) :marked In Angular 2, we use property binding; there is no built-in *href* directive. We place the element's `href` property in square brackets and set it to a quoted template expression. For more information on property binding see [Template Syntax](../guide/template-syntax.html#property-binding). In Angular 2, `href` is no longer used for routing. Routing uses `routerLink` as shown in the third example. +makeExample('cb-a1-a2-quick-reference/ts/app/app.component.html', 'router-link')(format="." ) :marked For more information on routing see [Routing & Navigation](../guide/router.html#router-link). tr(style=top) td :marked ### ng-if code-example(format=""). <table ng-if="movies.length"> :marked In Angular 1, the `ng-if` directive removes or recreates a portion of the DOM based on an expression. If the expression is false, the element is removed from the DOM. In this example, the `table` element is removed from the DOM unless the `movies` array has a length greater than zero. td :marked ### *ngIf +makeExample('cb-a1-a2-quick-reference/ts/app/movie-list.component.html', 'ngIf')(format="." ) :marked The `*ngIf` directive in Angular 2 works the same as the `ng-if` directive in Angular 1, it removes or recreates a portion of the DOM based on an expression. In this example, the `table` element is removed from the DOM unless the `movies` array has a length. The (*) before `ngIf` is required in this example. For more information see [Structural Directives](../guide/structural-directives.html). tr(style=top) td :marked ### ng-model code-example(format=""). <input ng-model="vm.favoriteHero"/> :marked In Angular 1, the `ng-model` directive binds a form control to a property in the controller associated with the template. This provides **two-way binding** whereby any changes made to the value in the view is synchronized with the model and any changes to the model are synchronized with the value in the view. td :marked ### ngModel +makeExample('cb-a1-a2-quick-reference/ts/app/movie-list.component.html', 'ngModel')(format="." ) :marked In Angular 2, **two-way binding** is denoted with [()], descriptively referred to as a "banana in a box". This syntax is a short-cut for defining both property binding (from the component to the view) and event binding (from the view to the component), thereby giving us two-way binding. For more information on two-way binding with ngModel see [Template Syntax](../guide/template-syntax.html#ngModel). tr(style=top) td :marked ### ng-repeat code-example(format=""). <tr ng-repeat="movie in vm.movies"> :marked In Angular 1, the `ng-repeat` directive repeats the associated DOM element for each item from the specified collection. In this example, the table row (`tr`) element is repeated for each movie object in the collection of movies. td :marked ### *ngFor +makeExample('cb-a1-a2-quick-reference/ts/app/movie-list.component.html', 'ngFor')(format="." ) :marked The `*ngFor` directive in Angular 2 is similar to the `ng-repeat` directive in Angular 1. It repeats the associated DOM element for each item from the specified collection. More accurately, it turns the defined element (`tr` in this example) and its contents into a template and uses that template to instantiate a view for each item in the list. Notice the other syntax differences: The (*) before `ngFor` is required; the (#) identifies `movie` as a local variable; the list preposition is `of`, not `in`. For more information see [Structural Directives](../guide/structural-directives.html). tr(style=top) td :marked ### ng-show code-example(format=""). <h3 ng-show="vm.favoriteHero"> Your favorite hero is: {{vm.favoriteHero}} </h3> :marked In Angular 1, the `ng-show` directive shows or hides the associated DOM element based on an expression. In this example, the `div` element is shown if the `favoriteHero` variable is truthy. td :marked ### bind to the `hidden` property +makeExample('cb-a1-a2-quick-reference/ts/app/movie-list.component.html', 'hidden')(format="." ) :marked In Angular 2, we use property binding; there is no built-in *show* directive. For hiding and showing elements, we bind to the HTML `hidden` property. To conditionally display an element, place the element's `hidden` property in square brackets and set it to a quoted template expression that evaluates to the *opposite* of *show*. In this example, the `div` element is hidden if the `favoriteHero` variable is not truthy. For more information on property binding see [Template Syntax](../guide/template-syntax.html#property-binding). tr(style=top) td :marked ### ng-src code-example(format=""). <img ng-src="{{movie.imageurl}}"> :marked The `ng-src` directive allows Angular 1 to preprocess the `src` property so it can replace the binding expression with the appropriate URL before the browser fetches from that URL. td :marked ### bind to the `src` property +makeExample('cb-a1-a2-quick-reference/ts/app/app.component.html', 'src')(format="." ) :marked In Angular 2, we use property binding; there is no built-in *src* directive. We place the `src` property in square brackets and set it to a quoted template expression. For more information on property binding see [Template Syntax](../guide/template-syntax.html#property-binding). tr(style=top) td :marked ### ng-style code-example(format=""). <div ng-style="{color: colorPreference}"> :marked In Angular 1, the `ng-style` directive sets a CSS style on an HTML element based on an expression. That expression is often a key-value control object with each key of the object defined as a CSS style name, and each value defined as an expression that evaluates to a value appropriate for the style. In the example, the `color` style is set to the current value of the `colorPreference` variable. td :marked ### ngStyle +makeExample('cb-a1-a2-quick-reference/ts/app/app.component.html', 'ngStyle')(format="." ) :marked In Angular 2, the `ngStyle` directive works similarly. It sets a CSS style on an HTML element based on an expression. In the first example, the `color` style is set to the current value of the `colorPreference` variable. Angular 2 also has **style binding**, which is good way to set a single style. This is shown in the second example. For more information on style binding see [Template Syntax](../guide/template-syntax.html#style-binding). For more information on the ngStyle directive see [Template Syntax](../guide/template-syntax.html#ngStyle). tr(style=top) td :marked ### ng-switch code-example(format=""). <div ng-switch="vm.favoriteHero && vm.checkMovieHero(vm.favoriteHero)"> <div ng-switch-when="true"> Excellent choice! </div> <div ng-switch-when="false"> No movie, sorry! </div> <div ng-switch-default> Please enter your favorite hero. </div> </div> :marked In Angular 1, the `ng-switch` directive swaps the contents of an element by selecting one of the templates based on the current value of an expression. In this example, if `favoriteHero` is not set, the template displays "Please enter ...". If the `favoriteHero` is set, it checks the movie hero by calling a controller method. If that method returns `true`, the template displays "Excellent choice!". If that methods returns `false`, the template displays "No movie, sorry!". td :marked ### ngSwitch +makeExample('cb-a1-a2-quick-reference/ts/app/movie-list.component.html', 'ngSwitch')(format="." ) :marked In Angular 2, the `ngSwitch` directive works similarly. It displays an element whose `*ngSwitchWhen` matches the current `ngSwitch` expression value. In this example, if `favoriteHero` is not set, the `ngSwitch` value is `null` and we see the `*ngSwitchDefault` paragraph, "Please enter ...". If the `favoriteHero` is set, it checks the movie hero by calling a component method. If that method returns `true`, we see "Excellent choice!". If that methods returns `false`, we see "No movie, sorry!". The (*) before `ngSwitchWhen` and `ngSwitchDefault` is required in this example. For more information on the ngSwitch directive see [Template Syntax](../guide/template-syntax.html#ngSwitch). :marked [Back to top](#top) a(id="filters-pipes") .l-main-section :marked ## Filters / Pipes Angular 2 **pipes** provide formatting and transformation for data in our template, similar to Angular 1 **filters**. Many of the built-in filters in Angular 1 have corresponding pipes in Angular 2. For more information on pipes see [Pipes](../guide/pipes.html). table(width="100%") col(width="50%") col(width="50%") tr th Angular 1 th Angular 2 tr(style=top) td :marked ### currency code-example. <td>{{movie.price | currency}}</td> :marked Formats a number as a currency. td :marked ### currency +makeExample('cb-a1-a2-quick-reference/ts/app/app.component.html', 'currency')(format="." ) :marked The Angular 2 `currency` pipe is similar although some of the parameters have changed. tr(style=top) td :marked ### date code-example. <td>{{movie.releaseDate | date}}</td> :marked Formats a date to a string based on the requested format. td :marked ### date +makeExample('cb-a1-a2-quick-reference/ts/app/app.component.html', 'date')(format=".") :marked The Angular 2 `date` pipe is similar. See [note](#string-dates) about string date values. tr(style=top) td :marked ### filter code-example. <tr ng-repeat="movie in movieList | filter: {title:listFilter}"> :marked Selects a subset of items from the defined collection based on the filter criteria. td :marked ### none There is no comparable pipe in Angular 2 for performance reasons. Filtering should be coded in the component. Consider building a custom pipe if the same filtering code will be reused in several templates. tr(style=top) td :marked ### json code-example. <pre>{{movie | json}}</pre> :marked Converts a JavaScript object into a JSON string. This is useful for debugging. td :marked ### json +makeExample('cb-a1-a2-quick-reference/ts/app/app.component.html', 'json')(format=".") :marked The Angular 2 `json` pipe does the same thing. tr(style=top) td :marked ### limitTo code-example. <tr ng-repeat="movie in movieList | limitTo:2:0"> :marked Selects up to the first parameter (2) number of items from the collection starting (optionally) at the beginning index (0). td :marked ### slice +makeExample('cb-a1-a2-quick-reference/ts/app/app.component.html', 'slice')(format=".") :marked The `SlicePipe` does the same thing but the *order of the parameters is reversed* in keeping with the JavaScript `Slice` method. The first parameter is the starting index; the second is the limit. As in Angular 1, performance may improve if we code this operation within the component instead. tr(style=top) td :marked ### lowercase code-example. <div>{{movie.title | lowercase}}</div> :marked Converts the string to lowercase. td :marked ### lowercase +makeExample('cb-a1-a2-quick-reference/ts/app/app.component.html', 'lowercase')(format=".") :marked The Angular 2 `lowercase` pipe does the same thing. tr(style=top) td :marked ### number code-example. <td>{{movie.starRating | number}}</td> :marked Formats a number as text. td :marked ### number +makeExample('cb-a1-a2-quick-reference/ts/app/app.component.html', 'number')(format=".") :marked The Angular 2 `number` pipe is similar. It provides more functionality when defining the decimal places as shown in the second example above. Angular 2 also has a `percent` pipe which formats a number as a local percentage as shown in the third example. tr(style=top) td :marked ### orderBy code-example. <tr ng-repeat="movie in movieList | orderBy : 'title'"> :marked Orders the collection as specified by the expression. In this example, the movieList is ordered by the movie title. td :marked ### none There is no comparable pipe in Angular 2 for performance reasons. Ordering/sorting the results should be coded in the component. Consider building a custom pipe if the same ordering/sorting code will be reused in several templates. :marked [Back to top](#top) a(id="controllers-components") .l-main-section :marked ## Controllers / Components In Angular 1, we write the code that provides the model and the methods for the view in a **controller**. In Angular 2, we build a **component**. Because much of our Angular 1 code is in JavaScript, JavaScript code is shown in the Angular 1 column. The Angular 2 code is shown using TypeScript. table(width="100%") col(width="50%") col(width="50%") tr th Angular 1 th Angular 2 tr(style=top) td :marked ### IIFE code-example. (function () { ... }()); :marked In Angular 1, we often defined an immediately invoked function expression (or IIFE) around our controller code. This kept our controller code out of the global namespace. td :marked ### none We don't need to worry about this in Angular 2 because we use ES 2015 modules and modules handle the namespacing for us. For more information on modules see [Architecture Overview](../guide/architecture.html#module). tr(style=top) td :marked ### Angular modules code-example. angular.module("movieHunter", ["ngRoute"]); :marked In Angular 1, we define an Angular module, which keeps track of our controllers, services, and other code. The second argument defines the list of other modules that this module depends upon. td :marked ### import +makeExample('cb-a1-a2-quick-reference/ts/app/movie-list.component.ts', 'import')(format=".") :marked Angular 2 does not have its own module system. Instead we use ES 2015 modules. ES 2015 modules are file based, so each code file is its own module. We `import` what we need from the module files. For more information on modules see [Architecture Overview](../guide/architecture.html#module). tr(style=top) td :marked ### Controller registration code-example. angular .module("movieHunter") .controller("MovieListCtrl", ["movieService", MovieListCtrl]); :marked In Angular 1, we have code in each controller that looks up an appropriate Angular module and registers the controller with that module. The first argument is the controller name. The second argument defines the string names of all dependencies injected into this controller, and a reference to the controller function. td :marked ### Component Decorator +makeExample('cb-a1-a2-quick-reference/ts/app/movie-list.component.ts', 'component')(format=".") :marked In Angular 2, we add a decorator to the component class to provide any required metadata. The Component decorator declares that the class is a component and provides metadata about that component, such as its selector (or tag) and its template. This is how we associate a template with code, which is defined in the component class. For more information on components see [Architecture Overview](../guide/architecture.html#component). tr(style=top) td :marked ### Controller function code-example. function MovieListCtrl(movieService) { } :marked In Angular 1, we write the code for the model and methods in a controller function. td :marked ### Component class +makeExample('cb-a1-a2-quick-reference/ts/app/movie-list.component.ts', 'class')(format=".") :marked In Angular 2, we create a component class. NOTE: If you are using TypeScript with Angular 1 then the only difference here is that the component class must be exported using the `export` keyword. For more information on components see [Architecture Overview](../guide/architecture.html#component). tr(style=top) td :marked ### Dependency injection code-example. MovieListCtrl.$inject = ['MovieService']; function MovieListCtrl(movieService) { } :marked In Angular 1, we pass in any dependencies as controller function arguments. In this example, we inject a `MovieService`. We also guard against minification problems by telling Angular explicitly that it should inject an instance of the `MovieService` in the first parameter. td :marked ### Dependency injection +makeExample('cb-a1-a2-quick-reference/ts/app/movie-list.component.ts', 'di')(format=".") :marked In Angular 2, we pass in dependencies as arguments to the component class constructor. In this example, we inject a `MovieService`. The first parameter's TypeScript type tells Angular what to inject even after minification. For more information on dependency injection see [Architecture Overview](../guide/architecture.html#dependency-injection). :marked [Back to top](#top) a(id="style-sheets") .l-main-section :marked ## Style Sheets Style sheets give our application a nice look. In Angular 1, we specify the style sheets for our entire application. As the application grows over time, the styles for the many parts of the application are merged, which can cause unexpected results. In Angular 2, we can still define style sheets for our entire application. But now we can also encapculate a style sheet within a specific component. table(width="100%") col(width="50%") col(width="50%") tr th Angular 1 th Angular 2 tr(style=top) td :marked ### Link tag code-example. <link href="styles.css" rel="stylesheet" /> :marked In Angular 1, we use a `link` tag in the head section of our `index.html` file to define the styles for our application. td :marked ### Link tag +makeExample('cb-a1-a2-quick-reference/ts/index.html', 'style')(format=".") :marked In Angular 2, we can continue to use the link tag to define the styles for our application in the `index.html` file. But we can now also encapsulate styles for our components. :marked ### StyleUrls In Angular 2, we can use the `styles` or `styleUrls` property of the `@Component` metadata to define a style sheet for a particular component. +makeExample('cb-a1-a2-quick-reference/ts/app/movie-list.component.ts', 'style-url')(format=".") :marked This allows us to set appropriate styles for individual components that won’t leak into other parts of the application. :marked [Back to top](#top) a(id="string-dates") .l-main-section :marked ## Appendix: String dates Currently the Angular 2 `date` pipe does not process string dates such as "2015-12-19T00:00:00". As a work around, subclass the Angular `DatePipe` with a version that can convert strings and substitute that pipe in the HTML: +makeExample('cb-a1-a2-quick-reference/ts/app/date.pipe.ts', 'date-pipe', 'date.pipe.ts')(format=".") :marked Then import and declare that pipe in the `@Component` metadata `pipes` array: :marked +makeExample('cb-a1-a2-quick-reference/ts/app/movie-list.component.ts', 'date-pipe')(format=".") :marked [Back to top](#top)