angular-docs-cn/public/docs/js/latest/cookbook/ts-to-js.jade

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

:marked
  Everything that we can do in Angular 2 in TypeScript, we can also do
  in JavaScript. Translating from one language to the other is mostly a
  matter of changing the way we organize our code and the way we access
  Angular 2 APIs.
  
  所有能在TypeScript环境里面做的Angular 2事情，我们都能在JavaScript里面实现。
  从一个语言翻译到另一个语言最多只能改变我们对源代码的管理方法和如何访问Angular 2的API。

  Since TypeScript is a popular language option in Angular 2, many of the
  code examples you see on the Internet as well as on this site are written
  in TypeScript. This cookbook contains recipes for translating these kinds of
  code examples to ES5, so that they can be applied to Angular 2 JavaScript
  applications.
  
  因为TypeScript是一个很受欢迎的Angular 2的语言选择，你在网络上和本站看到的很多代码例子
  都是以TypeScript编写的。本烹饪宝典包含如何把这些代码编译到ES5的食谱，这样它们可以被应用
  到Angular 2的JavaScript应用程序里。
  

<a id="toc"></a>
:marked
  ## Table of contents
  
  ## 目录

  [Modularity: imports and exports](#modularity)
  
  [模块化：导入和导出](#modularity)

  [Classes and Class Metadata](#class-metadata)
  
  [类和类元数据](#class-metadata)
  
  [Input and Output Metadata](#property-metadata)
  
  [导入和导出元数据](#property-metadata)
  
  [Dependency Injection](#dependency-injection)
  
  [依赖注入](#dependency-injection)
  
  [Host and Query Metadata](#other-property-metadata)
  
  [宿主和查询元素据](#other-property-metadata)

  **Run and compare the live [TypeScript](/resources/live-examples/cb-ts-to-js/ts/plnkr.html) and 
  [JavaScript](/resources/live-examples/cb-ts-to-js/js/plnkr.html) code shown in this cookbook.**
  
  **运行并比较本烹饪宝典里面的在线[TypeScript](/resources/live-examples/cb-ts-to-js/ts/plnkr.html)和[JavaScript](/resources/live-examples/cb-ts-to-js/js/plnkr.html)代码**

a(id="modularity")
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:marked
  ## Importing and Exporting

  ## 导入和导出

- var top="vertical-align:top"
table(width="100%")
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    th TypeScript
    th ES5 JavaScript
  tr(style=top)
    td
      :marked
        ### Importing Angular 2 Code

        ### 导入Angular 2代码

        In TypeScript code, Angular 2 classes, functions, and other members
        are imported with TypeScript `import` statements:
        
        在TypeScript代码中，Angular 2是利用TypeScript的`import`声明来导入类、函数和其他成员的。

      +makeExample('cb-ts-to-js/ts/app/main.ts', 'ng2import')(format="." )

    td
      :marked
        ### Accessing Angular 2 Code through the ng global
        
        ### 通过全局ng来访问Angular 2代码

        In JavaScript code, when using
        [the Angular 2 packages](../glossary.html#!#scoped-package),
        we can access Angular code through the global `ng` object. In the
        nested members of this object we'll find everything we would import
        from `angular2` in TypeScript:
        
        在JavaScript代码中，当使用[Angular 2库](../glossary.html#!#scoped-package)时，
        我们可以通过全局的`ng`对象来访问Angular代码。在这个对象嵌套很多成员中，我们能找到所有在TypeScript里面导入的`angular2`

      +makeExample('cb-ts-to-js/js/app/main.js', 'ng2import')(format="." )

  tr(style=top)
    td
      :marked
        ### Importing and Exporting Application Code

        ### 导入和导出应用程序代码

        Each file in an Angular 2 TypeScript application constitutes a
        TypeScript module. When we want to make something from a module available
        to other modules, we `export` it.
        
        在Angular 2 TypeScript应用里，每个文件组成一个TypeScript模块。当需要让一个模块在其他模块中可见时，我们`export`它。

      +makeExample('cb-ts-to-js/ts/app/hero.component.ts', 'appexport')(format="." )

      :marked
        In other modules we can then `import` things that have been exported
        elsewhere.
        
        然后，我们就可以在模块`import`其它地方导出的东西。

      +makeExample('cb-ts-to-js/ts/app/main.ts', 'appimport')(format="." )

    td
      :marked
        ### Sharing Application Code

        ### 共享应用程序代码

        In an Angular 2 JavaScript application, we load each file to the page
        using a `<script>` tag. Each file can make things available to other
        files via the shared global `window` scope.
        
        在Angular 2 JavaScript应用程序里，我们在页面里面通过`<script>`标签来加载每个文件。
        每个文件都能通过把所有东西放到全局`window`来互相共享·

        We often introduce an application namespace
        object (such as `"app"`) onto `window` and attach everything we need
        to share to that namespace object. 
        We also wrap our code in an 
        [Immediately Invoked Function Expression (IIFE)](https://en.wikipedia.org/wiki/Immediately-invoked_function_expression).
        These practices together prevent our code from
        polluting the global scope.
        
        我们经常在`window`上附加一个应用程序命名空间对象（比如`"app"`），然后把所有需要共享的东西都附加到这个空间对象。
        也可以把我们的代码包装到一个[立即调用函数表达式IIFE](https://en.wikipedia.org/wiki/Immediately-invoked_function_expression)。
        使用这些实践可以防止我们的代码污染全局范围。

      +makeExample('cb-ts-to-js/js/app/hero.component.js', 'appexport')(format="." )

      :marked
        We can then access anything from this shared namespace in
        other files.
        
        然后我们就可以从这个共享的命名空间来访问其他文件。

      +makeExample('cb-ts-to-js/js/app/main.js', 'appimport')(format="." )

      :marked
        Note that the order of `<script>` tags on the page is significant. 
        We must load a file that defines a shared member before
        a file that uses that member.
        
        注意，页面上的`<script>`标签的顺序非常重要。我们必须要先加载定义共享成员的文件，
        然后再加载使用该共享成员的文件。

.alert.is-helpful
  :marked
    Alternatively, we can use a module loader such as Webpack or
    Browserify in an Angular 2 JavaScript project. In such a project, we would
    use CommonJS modules and the `require` function to load Angular 2 framework code.
    We would then use `module.exports` and `require` to export and import application
    code.
    
    另外，我们可以在一个Angular 2 JavaScript项目中，使用模块加载器(比如Webpack或者Browserify)。
    在这样的项目中，我们使用CommonJS模块和`require`函数来加载Angular 2框架代码。
    然后用`module.exports`和`require`来导出和导入应用程序代码。


a(id="class-metadata")
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:marked
  ## Classes and Class Metadata

  ## 类和类元数据

- var top="vertical-align:top"
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    th TypeScript
    th ES5 JavaScript
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      :marked
        ### Classes
        
        ### 类

        We put most of our Angular 2 TypeScript code into TypeScript classes.
        
        我们把绝大多数Angular 2 TypeScript代码放到TypeScript类中。

      +makeExample('cb-ts-to-js/ts/app/hero.component.ts', 'class')(format="." )

    td
      :marked
        ### Constructors and Prototypes

        ### 构造函数和原型

        ES5 JavaScript has no classes. We use the constructor
        pattern instead which works with Angular 2 as well as classes do.
        
        ES5 JavaScript不支持类。取而代之，我们使用构造模式（constructor pattern），和类一样，它可以跟Angular 2一起工作。

      +makeExample('cb-ts-to-js/js/app/hero.component.js', 'constructorproto')(format="." )

  tr(style=top)
    td
      :marked
        ### Metadata with Decorators

        ### 拥有装饰器的元数据

        Most Angular 2 classes have one or more TypeScript *decorators*
        attached to provide configuration and metadata. For example,
        a component must have a [`@Component`](../api/core/Component-decorator.html) decorator.     
        
        大部分Angular 2的类都有一个或者多个附加的TypeScript*装饰器*，用来提供配置和元数据。比如一个组件必须要有一个[`@Component`](../api/core/Component-decorator.html)装饰器。
        
      +makeExample('cb-ts-to-js/ts/app/hero.component.ts', 'metadata')(format="." )

    td
      :marked
        ### Metadata with the Annotations Array
        
        通过注解数组来提供元数据        

        In JavaScript, we can attach an `annotations` array to a constructor
        to provide metadata. 
        Each item in the array corresponds to a TypeScript decorator.
        
        在JavaScript里，我们可以为构造函数附加一个`注解`数组来提供元数据。
        数组里的每一条项目对应一个TypeScript装饰器。

        In the following example, we create a new instance of `Component` that corresponds
        to the [`@Component`](../api/core/Component-decorator.html) TypeScript decorator.
        
        在下面的例子中，我们新建了一个`Component`的新实例，与[`@Component`](../api/core/Component-decorator.html)TypeScript装饰器对应。

      +makeExample('cb-ts-to-js/js/app/hero.component.js', 'metadata')(format="." )

      :marked
        ### Metadata with The Class Convenience API
        
        ### 通过类便利API来提供元素据

        The pattern of creating a constructor and decorating it with metadata
        is so common that Angular provides an alternative convenience API for it.
        This API lets us define everything in a single expression.
        
        新建一个构造函数并用元数据来装饰它的模式非常常见，以至于Angular为它提供了一个可选便利API。
        该API可以让我们只用单一表达式，就可以定义任何东西。

        With this API we first call the `ng.core.Component` function,
        followed by a chained `Class` method call. The argument to `Class`
        is an object that defines the constructor and the instance methods
        of the component:
        
        利用该API，我们先调用`ng.core.Component`函数，链接一个`Class`方法。该`Class`方法的参数是一个对象，
        用来定义组件的构造函数和实例方法。

      +makeExample('cb-ts-to-js/js/app/hero-dsl.component.js', 'component')(format="." )

      :marked
        Similar APIs are also available for other decorators. You can define a
        directive:
        
        其他装饰器也有类似的API。你可以像这样定义一个指令：
        
      code-example.
        var MyDirective = ng.core.Directive({
          ...
        }).Class({
          ...
        });
      
      :marked
        Or a pipe:
        
        或则一个管道：
        
      code-example.
        var MyPipe = ng.core.Pipe({
          name: 'myPipe'
        }).Class({
          ...
        });

  tr(style=top)
    td
      :marked
        ### Interfaces
        
        ### 接口

        When defining classes that need to implement a certain method, it
        is common to use TypeScript interfaces that enforce that the 
        method signature is correct. Component lifecycle methods like `ngOnInit`
        are one example of this pattern. `ngOnInit` is defined in the `OnInit`
        interface.
        
        当定义一个实现某个方法的类时，使用TypeScript接口来确保方法的签名正确是常见的手段。组件生命周期方法，比如`ngOnInit`是这个模式的其中一个例子。
        `ngOnInit`是在`OnInit`接口里面定义的。

      +makeExample('cb-ts-to-js/ts/app/hero-lifecycle.component.ts')(format="." )

    td
      :marked
        ### Implementing Methods without Interfaces
        
        ### 实现方法，但忽略接口

        TypeScript interfaces are purely for developer convenience
        and are not used by Angular 2 at runtime. This means that in JavaScript
        code we don't need to substitute anything for interfaces. We can just
        implement the methods.
        
        TypeScript接口是纯为开发者的方便服务的，它不能被Angular 2在运行时使用。这就意味着在JavaScript代码里面，
        我们不需要使用任何东西来代替接口。我们可以直接实现方法。

      +makeExample('cb-ts-to-js/js/app/hero-lifecycle.component.js')(format="." )

a(id="property-metadata")
.l-main-section
:marked
  ## Input and Output Metadata
  
  ## 输入和输出元素据

- var top="vertical-align:top"
table(width="100%")
  col(width="50%")
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  tr
    th TypeScript
    th ES5 JavaScript
  tr(style=top)
    td
      :marked
        ### Input and Output Decorators
        
        ### 输入和输出装饰器

        In TypeScript, property decorators are often used to provide additional metadata
        for components and directives.
        
        在TypeScript里，属性装饰器经常被用来为组件和指令提供额外的元素据。

        For [inputs and outputs](../guide/template-syntax.html#inputs-outputs), 
        we use [`@Input`](../api/core/Input-var.html)
        and [`@Output`](../api/core/Output-var.html) property decorators.
        They may optionally specify input and output binding names if we want them to be
        different from the class property names.
        
        我们使用[`@Input`](../api/core/Input-var.html) 和 [`@Output`](../api/core/Output-var.html)装饰器
        来装饰[输入和输出](../guide/template-syntax.html#inputs-outputs)。
        如果我们想要他们有与类属性名字不同的名字，我们可以选择性的指定输入和输出的绑定名字。

      +makeExample('cb-ts-to-js/ts/app/hero-io.component.ts')(format="." )

      .alert.is-helpful
        :marked
          In TypeScript we can also use the `inputs` and `outputs` array metadata 
          instead of the `@Input` and `@Output` property decorators.
          
          在TypeScript里，我们也可以使用`inputs`和`outputs`元数据数组，来取代`@Input`和`@Output`属性装饰器。
    td
      :marked
        ### Inputs and Outputs in Component Metadata
        
        ### 组件元数据里的输入和输出

        There is no equivalent of a property decorator in ES5 JavaScript. Instead, 
        we add comparable information to the `Component` (or `Directive`) metadata.
        
        在ES5 JavaScript里面没有对等的属性装饰器。取而代之，我们可以添加类似信息到`组件`（或者`指令`）的元数据。
        
        In this example, we add `inputs` and `outputs` array attributes
        containing the input and output property names. 
        If we need a binding name that is different from the
        property itself, we use the `propertyName: bindingName` syntax.
        
        在这个例子中，我们添加`inputs`和`outputs`数组属性，它们包含了输入和输出的属性名字。
        如果我们需要一个与属性名字不同的绑定名字，我们可以使用`propertyName: bindingName`的语法。

      +makeExample('cb-ts-to-js/js/app/hero-io.component.js')(format="." )


.l-main-section
:marked
  ## Dependency Injection
  
  ## 依赖注入

- var top="vertical-align:top"
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      :marked
        ### Injection by Type
        
        ### 按类型注入 

        Angular 2 can often use TypeScript type information to
        determine what needs to be injected.
        
        Angular 2可以经常使用TypeScript的类型信息来确定需要注入什么。

      +makeExample('cb-ts-to-js/ts/app/hero-di.component.ts')(format="." )

    td
      :marked
        ### Injection with Parameter Tokens
        
        ### 使用参数指令来注入

        Since no type information is available in ES5 JavaScript,
        we must identify "injectables" in some other way.
        
        因为在ES5 JavaScript里没有类型信息，所以我们必须要使用其他方法来识别“可以注入”的东西。

        We attach a `parameters` array to the constructor function. 
        Each array item is the dependency injection token that identifies the thing to be injected. 
        Often the token is the constructor function for the class-like dependency.
        
        我们给构造函数附加一个`参数`数组。每个数组项目都是一个依赖注入的令牌，用来识别被注入的东西。

      +makeExample('cb-ts-to-js/js/app/hero-di.component.js')(format="." )

      :marked
        When using the class convenience API, we can also supply the parameter
        tokens by wrapping the constructor in an array.
        
        当我们使用类便利API时，我们也可以把构造器包装到一个数组里面来提供参数令牌。

      +makeExample('cb-ts-to-js/js/app/hero-di-inline.component.js')(format="." )

  tr(style=top)
    td
      :marked
        ### Injection with the @Inject decorator
        
        ### 使用@Inject装饰器来注入

        When the thing being injected doesn't correspond directly to a type,
        we use the `@Inject()` decorator to supply the injection token.
        
        当被注入的东西不是一个类型时，我们使用`@inject()`装饰器来提供注入令牌。
        
        In this example, we're injecting a string identified by the "heroName" token.
        
        在这个例子中，通过令牌"heroName"，我们注入了一个字符串。

      +makeExample('cb-ts-to-js/ts/app/hero-di-inject.component.ts')(format="." )

    td
      :marked
        ### Injection with plain string tokens
        
        ### 利用字符串令牌来注入

        In JavaScript we add the token string to the injection parameters array.
        
        在JavaScript里，我们添加令牌字符串到注入参数数组中。

      +makeExample('cb-ts-to-js/js/app/hero-di-inject.component.js','parameters')(format="." )
      
      :marked
        Alternatively, we can create a token with the `Inject` method and
        add that to the constructor array in the annotations like this:
        
        另外，我们可以使用`Inject`方法来新建一个令牌，像这样把它加到注解的constructor数组中：
        
      +makeExample('cb-ts-to-js/js/app/hero-di-inject.component.js','ctor')(format="." )        

  tr(style=top)
    td
      :marked
        ### Additional Injection Decorators
        
        ### 额外注入装饰器

        We can attach additional decorators to constructor parameters
        to qualify the injection behavior. We can mark
        optional dependencies with the [`@Optional`](../api/core/Optional-var.html),
        inject host element attributes with [`@Attribute`](../api/core/Attribute-var.html),
        inject content child queries with [`@Query`](../api/core/Query-var.html)
        and inject view child queries with [`@ViewQuery`](../api/core/ViewQuery-var.html).
        
        我们可以附加额外装饰器到构造函数来调整注入行为。我们使用[`@Optional`](../api/core/Optional-var.html)来标示依赖是可选的，
        用[`@Attribute`](../api/core/Attribute-var.html)标示注入宿主元素属性
        用[`@Query`](../api/core/Query-var.html)来注入内容子查询，用[`@ViewQuery`](../api/core/ViewQuery-var.html)来注入视图子查询。

      +makeExample('cb-ts-to-js/ts/app/hero-di-inject-additional.component.ts')(format="." )

    td
      :marked
        ### Additional Injection Metadata with Nested Arrays 
        
        ### 利用嵌套数组来处理额外注入元数据

        To achieve the same effect in JavaScript, use the constructor array notation
        in which the injection information precedes the constructor function itself.
        
        在JavaScript，为了达到一样的效果，使用构造数组表示法，在其中，注入信息优先于构造函数自己本身。
        
        Use the injection support functions `Attribute`, `Host`, `Optional`, `Self`, `SkipSelf`,
        `Query` and `ViewQuery` to qualify dependency injection behavior.
        
        使用注入的支持功能比如`Attribute`、 `Host`、 `Optional`、 `Self`、 `SkipSelf`、
        `Query` 和 `ViewQuery`等来调整依赖注入行为。
        
        Use a nested array to combine injection functions.
        
        使用嵌套数组来合并注入函数。

      +makeExample('cb-ts-to-js/js/app/hero-di-inject-additional.component.js')(format="." )

      :marked
        We can apply other additional parameter decorators such as
        [`@Host`](../api/core/Host-var.html) and
        [`@SkipSelf`](../api/core/SkipSelf-var.html) in the same way -
        by adding `new ng.core.Host()` or `ng.core.SkipSelf()` in the
        parameters array.
        
        我们可以用同样的方法来应用其他额外的参数装饰器，比如[`@Host`](../api/core/Host-var.html) 和
        [`@SkipSelf`](../api/core/SkipSelf-var.html)：添加`new ng.core.Host()` 或 `ng.core.SkipSelf()`到参数数组中。


a(id="other-property-metadata")
.l-main-section
:marked
  ## Host and Query Metadata
  
  ## 宿主和查询元数据

- var top="vertical-align:top"
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    th ES5 JavaScript  
  tr(style=top)
  
    td
      :marked
        ### Host Decorators
        
        ### 宿主装饰器

        We can use host property decorators to bind a host element to a component or directive.
        The [`@HostBinding`](../api/core/HostBinding-var.html) decorator
        binds host element properties to component data properties. 
        The [`@HostListener`](../api/core/HostListener-var.html) decorator binds
        host element events to component event handlers.
        
        我们可以使用宿主属性装饰器来绑定一个宿主元素到一个组件或者指令。
        [`@HostBinding`](../api/core/HostBinding-var.html)装饰器绑定数组元素属性到组件数据属性。
         [`@HostListener`](../api/core/HostListener-var.html)装饰器绑定宿主元素事件到组件事件处理器。
        
      +makeExample('cb-ts-to-js/ts/app/heroes-bindings.component.ts')(format="." )
      
      .alert.is-helpful
        :marked
          In TypeScript we can also use `host` metadata 
          instead of the `@HostBinding` and `@HostListener` property decorators.
          
          在TypeScript，我们也可以使用`host`元数据来取代`@HostBinding`和`@HostListener`属性装饰器。
    td
      :marked
        ### Host Metadata
        
        ### Host元数据
        
        We add a `host` attribute to the component metadata to achieve the
        same effect as `@HostBinding` and `@HostListener`.
        
        我们添加一个`host`属性到组件元素据，来达到与`@HostBinding`和`@HostListener`一样的效果。 
        
        The  `host` value is an object whose properties are host property and listener bindings:
        
        `host`的值是一个对象，它属性包含了宿主属性和事件的绑定。
        
        * Each key follows regular Angular 2 binding syntax: `[property]` for host bindings
          or `(event)` for host listeners.
          
        * 每个键值（key）都遵循常规Angular 2绑定语法：`[property]`代表宿主属性绑定或`(event)`来代表数组事件绑定。
        
        * Each value identifies the corresponding component property or method.
        
        * 每个值（value）代表了对应的的组件属性和方法。
        
      +makeExample('cb-ts-to-js/js/app/heroes-bindings.component.js')(format="." )

  tr(style=top)
    td
      :marked
        ### Query Decorators
        
        ### 查询装饰器
        
        There are several property decorators for querying the descendants of
        a component or directive.
        
        用来查询组件和指令子级的属性装饰器有好几个。
        
        The [`@ViewChild`](../api/core/ViewChild-var.html) and 
        [`@ViewChildren`](../api/core/ViewChildren-var.html) property decorators
        allow a component to query instances of other components that are used in
        its view.
        
        [`@ViewChild`](../api/core/ViewChild-var.html)和
        [`@ViewChildren`](../api/core/ViewChildren-var.html)属性装饰器允许一个组件查询
        在自己模板里使用过的其他组件的实例。
        
        
      +makeExample('cb-ts-to-js/ts/app/heroes-queries.component.ts', 'view')(format="." )

      :marked
        The [`@ContentChild`](../api/core/ContentChild-var.html) and
        [`@ContentChildren`](../api/core/ContentChildren-var.html) property decorators
        allow a component to query instances of other components that have been projected
        into its view from elsewhere.
        
        [`@ContentChild`](../api/core/ContentChild-var.html) 和
        [`@ContentChildren`](../api/core/ContentChildren-var.html)属性装饰器允许一个组件查询
        被从其它地方投影进自己视图里的其他组件的实例。
        
      +makeExample('cb-ts-to-js/ts/app/heroes-queries.component.ts', 'content')(format="." )
      
      .alert.is-helpful
        :marked
          In TypeScript we can also use the `queries` metadata 
          instead of the `@ViewChild` and `@ContentChild` property decorators.
          
          在TypeScript我们也可以使用`queries`元数据来取代`@ViewChild`和`@ContentChild`属性装饰器。      
    td
      :marked
        ### Query Metadata
        
        ### 查询元数据
        
        We access a component's view children by adding a `queries` attribute to
        the component metadata. It should be an object where:
        
        我们通过添加`queries`属性到组件元数据来访问一个组件的视图子级。它应该是一个对象：
        
        * Each key is the name of a component property that will hold the view children
        
        * 每个键值（key）都是一个组件属性的名字，该属性是用来装载视图子级的。
        
        * Each value is an instance of either `ViewChild` or `ViewChildren`.
        
        * 每个值都是一个`ViewChild`或者`ViewChildren`实例。
        
      +makeExample('cb-ts-to-js/js/app/heroes-queries.component.js', 'view')(format="." )

      :marked
        We add *content* child queries to the same `queries` attribute
        in the same manner, using instances of `ContentChild` or `ContentChildren`:
        
        同样，我们利用`ContentChild`和`ContentChildren`来添加*content*子级查询到`queries`属性：
        
      +makeExample('cb-ts-to-js/js/app/heroes-queries.component.js', 'content')(format="." )