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关于AngularJS 与 Angular 概念的快速参考

AngularJS to Angular concepts: Quick reference

Angular 这个名字专指现在和未来的 Angular 版本,而 AngularJS 专指 Angular 的所有 v1.x 版本。

Angular is the name for the Angular of today and tomorrow. AngularJS is the name for all v1.x versions of Angular.

本章提供了一个快速的参考指南,指出一些常用的 AngularJS 语法及其在 Angular 中的等价物。

This guide helps you transition from AngularJS to Angular by mapping AngularJS syntax to the equivalent Angular syntax.

参见在线例子 / 下载范例以学习 Angular 语法

See the Angular syntax in this在线例子 / 下载范例.

模板基础

Template basics

模板是 Angular 应用中的门面部分,它是用 HTML 写的。下表中是一些 AngularJS 中的关键模板特性及其在 Angular 中的等价语法。

Templates are the user-facing part of an Angular application and are written in HTML. The following table lists some of the key AngularJS template features with their equivalent Angular template syntax.

AngularJS

Angular

绑定/插值

Bindings/interpolation

Your favorite hero is: {{vm.favoriteHero}}
      
      Your favorite hero is: {{vm.favoriteHero}}
    

在 AngularJS 中,花括号中的表达式代表单向绑定。 它把元素的值绑定到了与模板相关控制器的属性上。

In AngularJS, 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.

当使用 controller as 语法时,该绑定需要用控制器的别名(vm)为前缀,这是因为你不得不通过它来指定绑定源。

When using the controller as syntax, the binding is prefixed with the controller alias (vm or $ctrl) because you have to be specific about the source of the binding.

绑定/插值

Bindings/interpolation

Your favorite hero is: {{favoriteHero}}
      
      Your favorite hero is: {{favoriteHero}}
    

在 Angular 中,花括号中的模板表达式同样代表单向绑定。 它把元素的值绑定到了组件的属性上。 它绑定的上下文变量是隐式的,并且总是关联到组件。 所以,它不需要一个引用变量。

In Angular, 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.

要了解更多,请参见模板语法中的插值部分。

For more information, see the Interpolation section of the Template Syntax page.

过滤器

Filters

<td>{{movie.title | uppercase}}</td>
      
      <td>{{movie.title | uppercase}}</td>
    

要在 AngularJS 中过滤输出,使用管道字符(|)以及一个或多个过滤器。

To filter output in AngularJS templates, use the pipe character (|) and one or more filters.

这个例子中把 title 属性过滤成了大写形式。

This example filters the title property to uppercase.

管道

Pipes

<td>{{movie.title | uppercase}}</td>
      
      <td>{{movie.title | uppercase}}</td>
    

在 Angular 中,你使用类似的语法 —— 用管道字符(|)来过滤输出,但是现在直接把它叫做管道了。 很多(但不是所有)AngularJS 中的内置过滤器也成了 Angular 中的内置管道。

In Angular you use similar syntax with the pipe (|) character to filter output, but now you call them pipes. Many (but not all) of the built-in filters from AngularJS are built-in pipes in Angular.

请参见下面过滤器/管道了解更多信息。

For more information, see Filters/pipes below.

局部变量

Local variables

<tr ng-repeat="movie in vm.movies"> <td>{{movie.title}}</td> </tr>
      
      <tr ng-repeat="movie in vm.movies">
  <td>{{movie.title}}</td>
</tr>
    

这里的 movie 是一个用户定义的局部变量

Here, movie is a user-defined local variable.

输入变量

Input variables

<tr *ngFor="let movie of movies"> <td>{{movie.title}}</td> </tr>
      
      <tr *ngFor="let movie of movies">
  <td>{{movie.title}}</td>
</tr>
    

Angular 有了真正的模板输入变量,它需要使用 let 关键字进行明确定义。

Angular has true template input variables that are explicitly defined using the let keyword.

要了解更多信息,请参见模板语法中的ngFor 微语法部分。

For more information, see the ngFor micro-syntax section of the Template Syntax page.

模板指令

Template directives

AngularJS 为模板提供了七十多个内置指令。 在 Angular 中,它们很多都已经不需要了,因为 Angular 有了一个更加强大、快捷的绑定系统。 下面是一些 AngularJS 中的关键指令及其在 Angular 中的等价物。

AngularJS provides more than seventy built-in directives for templates. Many of them aren't needed in Angular because of its more capable and expressive binding system. The following are some of the key AngularJS built-in directives and their equivalents in Angular.

AngularJS

Angular

ng-app

<body ng-app="movieHunter">
      
      <body ng-app="movieHunter">
    

应用的启动过程被称为引导

The application startup process is called bootstrapping.

虽然可以从代码中引导 Angular 应用, 但很多应用都是通过 ng-app 指令进行声明式引导的,只要给它一个应用模块的名字(movieHunter)就可以了。

Although you can bootstrap an AngularJS app in code, many applications bootstrap declaratively with the ng-app directive, giving it the name of the application's module (movieHunter).

引导

Bootstrapping

import { enableProdMode } from '@angular/core'; import { platformBrowserDynamic } from '@angular/platform-browser-dynamic'; import { AppModule } from './app/app.module'; import { environment } from './environments/environment'; if (environment.production) { enableProdMode(); } platformBrowserDynamic().bootstrapModule(AppModule);
main.ts
      
      import { enableProdMode } from '@angular/core';
import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';

import { AppModule } from './app/app.module';
import { environment } from './environments/environment';

if (environment.production) {
  enableProdMode();
}

platformBrowserDynamic().bootstrapModule(AppModule);
    

import { NgModule } from '@angular/core'; import { BrowserModule } from '@angular/platform-browser'; import { AppComponent } from './app.component'; @NgModule({ imports: [ BrowserModule ], declarations: [ AppComponent ], bootstrap: [ AppComponent ] }) export class AppModule { }
app.module.ts
      
      import { NgModule }      from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';

import { AppComponent }  from './app.component';

@NgModule({
  imports: [ BrowserModule ],
  declarations: [ AppComponent ],
  bootstrap: [ AppComponent ]
})
export class AppModule { }
    

Angular 没有引导指令。 总是要通过显式调用一个 bootstrap 函数,并传入应用模块的名字(AppComponent)来启动应用。

Angular doesn't have a bootstrap directive. To launch the app in code, explicitly bootstrap the application's root module (AppModule) in main.ts and the application's root component (AppComponent) in app.module.ts.

ng-class

<div ng-class="{active: isActive}"> <div ng-class="{active: isActive, shazam: isImportant}">
      
      <div ng-class="{active: isActive}">
<div ng-class="{active: isActive,
                   shazam: isImportant}">
    

在 AngularJS 中,ng-class 指令会基于一个表达式来包含/排除某些 CSS 类。该表达式通常是一个“键-值”型的控制对象, 对象中的每一个键代表一个 CSS 类名,每一个值定义为一个返回布尔值的模板表达式。

In AngularJS, 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.

在第一个例子中,如果 isActive 为真,则 active 类被应用到那个元素上。

In the first example, the active class is applied to the element if isActive is true.

就像第二个例子中所展示的那样,可以同时指定多个类。

You can specify multiple classes, as shown in the second example.

ngClass

<div [ngClass]="{'active': isActive}"> <div [ngClass]="{'active': isActive, 'shazam': isImportant}"> <div [class.active]="isActive">
      
      <div [ngClass]="{'active': isActive}">
<div [ngClass]="{'active': isActive,
                 'shazam': isImportant}">
<div [class.active]="isActive">
    

在 Angular 中,ngClass 指令用类似的方式工作。 它根据一个表达式包含/排除某些 CSS 类。

In Angular, the ngClass directive works similarly. It includes/excludes CSS classes based on an expression.

在第一个例子中,如果 isActive 为真,则 active 类被应用到那个元素上。

In the first example, the active class is applied to the element if isActive is true.

就像第二个例子中所展示的那样,可以同时指定多个类。

You can specify multiple classes, as shown in the second example.

Angular 还有类绑定,它是单独添加或移除一个类的好办法 —— 就像第三个例子中展示的。

Angular also has class binding, which is a good way to add or remove a single class, as shown in the third example.

要了解更多信息,参见模板语法中的属性、CSS 类和样式绑定部分。

For more information see the Attribute, class, and style bindings section of the Template Syntax page.

ng-click

<button ng-click="vm.toggleImage()"> <button ng-click="vm.toggleImage($event)">
      
      <button ng-click="vm.toggleImage()">
<button ng-click="vm.toggleImage($event)">
    

在 AngularJS 中,ng-click 指令指定当元素被点击时的自定义行为。

In AngularJS, the ng-click directive allows you to specify custom behavior when an element is clicked.

在第一个例子中,如果用户点击了这个按钮,那么控制器的 toggleImage() 方法就会被执行,这个控制器是被 controller as 中指定的 vm 别名所引用的。

In the first example, when the user clicks the button, the toggleImage() method in the controller referenced by the vm controller as alias is executed.

第二个例子演示了传入 $event 对象,它提供了事件的详情,并被传到控制器。

The second example demonstrates passing in the $event object, which provides details about the event to the controller.

绑定到 click 事件

Bind to the click event

<button (click)="toggleImage()"> <button (click)="toggleImage($event)">
      
      <button (click)="toggleImage()">
<button (click)="toggleImage($event)">
    

AngularJS 基于事件的指令在 Angular 中已经不存在了。 不过,可以使用事件绑定来定义从模板视图到组件的单向数据绑定。

AngularJS event-based directives do not exist in Angular. Rather, define one-way binding from the template view to the component using event binding.

要使用事件绑定,把目标事件的名字放在圆括号中,并且使用等号右侧引号中的模板语句对它赋值。 然后 Angular 为这个目标时间设置事件处理器。当事件被触发时,这个处理器就会执行模板语句。

For event binding, define the name of the target event within parenthesis and specify a template statement, in quotes, to the right of the equals. Angular then sets up an event handler for the target event. When the event is raised, the handler executes the template statement.

在第一个例子中,当用户点击此按钮时,相关组件中的 toggleImage() 方法就被执行了。

In the first example, when a user clicks the button, the toggleImage() method in the associated component is executed.

第二个例子演示了如何传入 $event 对象,它为组件提供了此事件的详情。

The second example demonstrates passing in the $event object, which provides details about the event to the component.

要查看 DOM 事件的列表,请参见网络事件

For a list of DOM events, see: https://developer.mozilla.org/en-US/docs/Web/Events.

要了解更多,请参见模板语法中的事件绑定部分。

For more information, see the Event binding section of the Template Syntax page.

ng-controller

<div ng-controller="MovieListCtrl as vm">
      
      <div ng-controller="MovieListCtrl as vm">
    

在 AngularJS 中,ng-controller 指令把控制器附加到视图上。 使用 ng-controller(或把控制器定义为路由的一部分)把视图及其控制器的代码联系在一起。

In AngularJS, 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.

组件装饰器

Component decorator

@Component({ selector: 'app-movie-list', templateUrl: './movie-list.component.html', styleUrls: [ './movie-list.component.css' ], })
      
      @Component({
  selector: 'app-movie-list',
  templateUrl: './movie-list.component.html',
  styleUrls: [ './movie-list.component.css' ],
})
    

在 Angular 中,模板不用再指定它相关的控制器。 反过来,组件会在组件类的装饰器中指定与它相关的模板。

In Angular, the template no longer specifies its associated controller. Rather, the component specifies its associated template as part of the component class decorator.

要了解更多,请参见架构概览

For more information, see Architecture Overview.

ng-hide

在 AngularJS 中,ng-hide 指令会基于一个表达式显示或隐藏相关的 HTML 元素。 参见ng-show了解更多。

In AngularJS, the ng-hide directive shows or hides the associated HTML element based on an expression. For more information, see ng-show.

绑定到 hidden 属性

Bind to the hidden property

在 Angular 中,并没有一个内置的 hide 指令,可以改用属性绑定。 参见ng-show了解更多。

In Angular, you use property binding; there is no built-in hide directive. For more information, see ng-show.

ng-href

<a ng-href="{{ angularDocsUrl }}">Angular Docs</a>
      
      <a ng-href="{{ angularDocsUrl }}">Angular Docs</a>
    

ng-href 指令允许 AngularJS 对 href 属性进行预处理,以便它能在浏览器获取那个 URL 之前,使用一个返回适当 URL 的绑定表达式替换它。

The ng-href directive allows AngularJS to preprocess the href property so that it can replace the binding expression with the appropriate URL before the browser fetches from that URL.

在 AngularJS 中,ng-href 通常用来作为导航的一部分,激活一个路由。

In AngularJS, the ng-href is often used to activate a route as part of navigation.

<a ng-href="#{{ moviesHash }}">Movies</a>
      
      <a ng-href="#{{ moviesHash }}">Movies</a>
    

路由在 Angular 中的处理方式不同。

Routing is handled differently in Angular.

绑定到 href 属性

Bind to the href property

<a [href]="angularDocsUrl">Angular Docs</a>
      
      <a [href]="angularDocsUrl">Angular Docs</a>
    

在 Angular 中,并没有内置的 href 指令,改用属性绑定。 把元素的 href 属性放在方括号中,并把它设成一个引号中的模板表达式。

Angular uses property binding; there is no built-in href directive. Place the element's href property in square brackets and set it to a quoted template expression.

要了解属性绑定的更多知识,参见模板语法

For more information see the Property binding section of the Template Syntax page.

在 Angular 中,href 不再用作路由,而是改用第三个例子中所展示的 routerLink 指令。

In Angular, href is no longer used for routing. Routing uses routerLink, as shown in the following example.

<a [routerLink]="['/movies']">Movies</a>
      
      <a [routerLink]="['/movies']">Movies</a>
    

要了解关于路由的更多信息,请参见路由与导航RouterLink 绑定部分。

For more information on routing, see the RouterLink binding section of the Routing & Navigation page.

ng-if

<table ng-if="movies.length">
      
      <table ng-if="movies.length">
    

在 AngularJS 中,ng-if 指令会根据一个表达式来移除或重建 DOM 中的一部分。如果表达式为假,元素就会被从 DOM 中移除。

In AngularJS, 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.

在这个例子中,除非 movies 数组的长度大于 0,否则 <table> 元素就会被从 DOM 中移除。

In this example, the <table> element is removed from the DOM unless the movies array has a length greater than zero.

*ngIf

<table *ngIf="movies.length">
      
      <table *ngIf="movies.length">
    

Angular 中的 *ngIf 指令与 AngularJS 中的 ng-if 指令一样, 它根据表达式的值移除或重建 DOM 中的一部分。

The *ngIf directive in Angular works the same as the ng-if directive in AngularJS. It removes or recreates a portion of the DOM based on an expression.

在这个例子中,除非 movies 数组的长度大于 0,否则 <table> 元素就会被从 DOM 中移除。

In this example, the <table> element is removed from the DOM unless the movies array has a length.

在这个例子中 ngIf 前的星号(*)是必须的。 要了解更多信息,参见结构型指令

The (*) before ngIf is required in this example. For more information, see Structural Directives.

ng-model

<input ng-model="vm.favoriteHero"/>
      
      <input ng-model="vm.favoriteHero"/>
    

在 AngularJS 中,ng-model 指令把一个表单控件绑定到了模板相关控制器的一个属性上。 这提供了双向绑定功能,因此,任何对视图中值的改动,都会同步到模型中,对模型的改动,也会同步到视图中。

In AngularJS, 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 change made to the value in the view is synchronized with the model, and any change to the model is synchronized with the value in the view.

ngModel

<input [(ngModel)]="favoriteHero" />
      
      <input [(ngModel)]="favoriteHero" />
    

在 Angular 中,双向绑定使用[()]标记出来,它被形象的比作“盒子中的香蕉”。 这种语法是一个简写形式,用来同时定义一个属性绑定(从组件到视图)和一个事件绑定(从视图到组件),就成了双向绑定。

In Angular, two-way binding is denoted by [()], descriptively referred to as a "banana in a box". This syntax is a shortcut for defining both property binding (from the component to the view) and event binding (from the view to the component), thereby providing two-way binding.

要了解使用 ngModel 进行双向绑定的更多知识,参见模板语法中的NgModel—使用 [(ngModel)] 进行双向绑定部分。

For more information on two-way binding with ngModel, see the NgModel—Two-way binding to form elements with [(ngModel)]section of the Template Syntax page.

ng-repeat

<tr ng-repeat="movie in vm.movies">
      
      <tr ng-repeat="movie in vm.movies">
    

在 AngularJS 中,ng-repeat 指令会为指定集合中的每一个条目重复渲染相关的 DOM 元素。

In AngularJS, the ng-repeat directive repeats the associated DOM element for each item in the specified collection.

在这个例子中,对 movies 集合中的每一个 movie 对象重复渲染了这个表格行元素(<tr>)。

In this example, the table row (<tr>) element repeats for each movie object in the collection of movies.

*ngFor

<tr *ngFor="let movie of movies">
      
      <tr *ngFor="let movie of movies">
    

Angular 中的 *ngFor 指令类似于 AngularJS 中的 ng-repeat 指令。 它为指定集合中的每一个条目重复渲染了相关的 DOM 元素。 更准确的说,它把被界定出来的元素(这个例子中是 <tr>)及其内容转成了一个模板,并使用那个模板来为列表中的每一个条目实例化一个视图。

The *ngFor directive in Angular is similar to the ng-repeat directive in AngularJS. It repeats the associated DOM element for each item in 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.

请注意其它语法上的差异: 在 ngFor 前面的星号(*)是必须的;let 关键字把 movie 标记成一个输入变量;列表中使用的介词是 of,而不再是 in

Notice the other syntax differences: The (*) before ngFor is required; the let keyword identifies movie as an input variable; the list preposition is of, not in.

要了解更多信息,参见结构性指令

For more information, see Structural Directives.

ng-show

<h3 ng-show="vm.favoriteHero"> Your favorite hero is: {{vm.favoriteHero}} </h3>
      
      <h3 ng-show="vm.favoriteHero">
  Your favorite hero is: {{vm.favoriteHero}}
</h3>
    

在 AngularJS 中,ng-show 指令根据一个表达式来显示或隐藏相关的 DOM 元素。

In AngularJS, the ng-show directive shows or hides the associated DOM element, based on an expression.

在这个例子中,如果 favoriteHero 变量为真,<div> 元素就会显示出来。

In this example, the <div> element is shown if the favoriteHero variable is truthy.

绑定到 hidden 属性

Bind to the hidden property

<h3 [hidden]="!favoriteHero"> Your favorite hero is: {{favoriteHero}} </h3>
      
      <h3 [hidden]="!favoriteHero">
  Your favorite hero is: {{favoriteHero}}
</h3>
    

在 Angular 中,并没有内置的 show 指令,可以改用属性绑定。 要隐藏或显示一个元素,绑定到它的 hidden 属性就可以了。

Angular uses property binding; there is no built-in show directive. For hiding and showing elements, bind to the HTML hidden property.

要想有条件的显示一个元素,就把该元素的 hidden 属性放到一个方括号里,并且把它设置为引号中的模板表达式,它的结果应该是与显示相反的值。

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.

在这个例子中,如果 favoriteHero 变量不是真值,<div> 元素就会被隐藏。

In this example, the <div> element is hidden if the favoriteHero variable is not truthy.

要了解属性绑定的更多知识,参见模板语法中的属性绑定部分。

For more information on property binding, see the Property binding section of the Template Syntax page.

ng-src

<img ng-src="{{movie.imageurl}}">
      
      <img ng-src="{{movie.imageurl}}">
    

ng-src 指令允许 AngularJS 对 src 属性进行预处理,以便它能够在浏览器获取此 URL 之前,用一个返回适当 URL 的绑定表达式替换它。

The ng-src directive allows AngularJS to preprocess the src property so that it can replace the binding expression with the appropriate URL before the browser fetches from that URL.

绑定到 src 属性

Bind to the src property

<img [src]="movie.imageurl">
      
      <img [src]="movie.imageurl">
    

在 Angular 中,并没有一个内置的 src 指令,可以使用属性绑定。 把 src 属性放到方括号中,并且把它设为一个引号中的绑定表达式。

Angular uses property binding; there is no built-in src directive. Place the src property in square brackets and set it to a quoted template expression.

要了解关于属性绑定的更多知识,参见模板语法中的属性绑定部分。

For more information on property binding, see the Property binding section of the Template Syntax page.

ng-style

<div ng-style="{color: colorPreference}">
      
      <div ng-style="{color: colorPreference}">
    

在 AngularJS 中,ng-style 指令根据一个绑定表达式设置一个 HTML 元素的 CSS 样式。 该表达式通常是一个“键-值”形式的控制对象,对象的每个键都是一个 CSS 属性,每个值都是一个能计算为此样式的合适值的表达式。

In AngularJS, 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 property, and each value defined as an expression that evaluates to a value appropriate for the style.

在这个例子中,color 样式被设置为 colorPreference 变量的当前值。

In the example, the color style is set to the current value of the colorPreference variable.

ngStyle

<div [ngStyle]="{'color': colorPreference}"> <div [style.color]="colorPreference">
      
      <div [ngStyle]="{'color': colorPreference}">
<div [style.color]="colorPreference">
    

在 Angular 中,ngStyle 指令的工作方式与此类似。它根据一个表达式设置 HTML 元素上的 CSS 样式。

In Angular, the ngStyle directive works similarly. It sets a CSS style on an HTML element based on an expression.

在第一个例子中,color 样式被设置成了 colorPreference 变量的当前值。

In the first example, the color style is set to the current value of the colorPreference variable.

Angular 还有样式绑定语法,它是单独设置一个样式的好方法。它展示在第二个例子中。

Angular also has style binding, which is good way to set a single style. This is shown in the second example.

要了解关于样式绑定的更多知识,参见模板语法中的样式绑定部分。

For more information on style binding, see the Style binding section of the Template Syntax page.

要了解关于 ngStyle 指令的更多知识,参见模板语法中的NgStyle部分。

For more information on the ngStyle directive, see NgStyle section of the Template Syntax page.

ng-switch

<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>
      
      <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>
    

在 AngularJS 中,ng-switch 指令根据一个表达式的当前值把元素的内容替换成几个模板之一。

In AngularJS, the ng-switch directive swaps the contents of an element by selecting one of the templates based on the current value of an expression.

在这个例子中,如果 favoriteHero 没有设置,则模板显示“Please enter ...”。 如果 favoriteHero 设置过,它就会通过调用一个控制其方法来检查它是否电影里的英雄。 如果该方法返回 true,模板就会显示“Excellent choice!”。 如果该方法返回 false,该模板就会显示“No movie, sorry!”。

In this example, if favoriteHero is not set, the template displays "Please enter ...". If 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!".

ngSwitch

<span [ngSwitch]="favoriteHero && checkMovieHero(favoriteHero)"> <p *ngSwitchCase="true"> Excellent choice! </p> <p *ngSwitchCase="false"> No movie, sorry! </p> <p *ngSwitchDefault> Please enter your favorite hero. </p> </span>
      
      <span [ngSwitch]="favoriteHero &&
               checkMovieHero(favoriteHero)">
  <p *ngSwitchCase="true">
    Excellent choice!
  </p>
  <p *ngSwitchCase="false">
    No movie, sorry!
  </p>
  <p *ngSwitchDefault>
    Please enter your favorite hero.
  </p>
</span>
    

在 Angular 中,ngSwitch 指令的工作方式与此类似。 它会显示那个与 ngSwitch 表达式的当前值匹配的那个 *ngSwitchCase 所在的元素。

In Angular, the ngSwitch directive works similarly. It displays an element whose *ngSwitchCase matches the current ngSwitch expression value.

在这个例子中,如果 favoriteHero 没有设置,则 ngSwitch 的值是 null*ngSwitchDefault 中会显示 “Please enter ...”。 如果设置了 favoriteHero,应用就会通过调用一个组件方法来检查电影英雄。 如果该方法返回 true,就会显示 “Excellent choice!”。 如果该方法返回 false,就会显示 “No movie, sorry!”。

In this example, if favoriteHero is not set, the ngSwitch value is null and *ngSwitchDefault displays, "Please enter ...". If favoriteHero is set, the app checks the movie hero by calling a component method. If that method returns true, the app selects *ngSwitchCase="true" and displays: "Excellent choice!" If that methods returns false, the app selects *ngSwitchCase="false" and displays: "No movie, sorry!"

在这个例子中,ngSwitchCasengSwitchDefault 前面的星号(*)是必须的。

The (*) before ngSwitchCase and ngSwitchDefault is required in this example.

要了解更多信息,参见模板语法中的NgSwitch 指令部分。

For more information, see The NgSwitch directives section of the Template Syntax page.

过滤器/管道

Filters/pipes

Angular 中的管道为模板提供了格式化和数据转换功能,类似于 AngularJS 中的过滤器。 AngularJS 中的很多内置过滤器在 Angular 中都有对应的管道。 要了解管道的更多信息,参见Pipes

Angular pipes provide formatting and transformation for data in the template, similar to AngularJS filters. Many of the built-in filters in AngularJS have corresponding pipes in Angular. For more information on pipes, see Pipes.

AngularJS

Angular

currency

<td>{{movie.price | currency}}</td>
      
      <td>{{movie.price | currency}}</td>
    

把一个数字格式化成货币。

Formats a number as currency.

currency

<td>{{movie.price | currency:'USD':true}}</td>
      
      <td>{{movie.price | currency:'USD':true}}</td>
    

Angular 的 currency 管道和 1 中很相似,只是有些参数变化了。

The Angular currency pipe is similar although some of the parameters have changed.

date

<td>{{movie.releaseDate | date}}</td>
      
      <td>{{movie.releaseDate | date}}</td>
    

基于要求的格式把日期格式化成字符串。

Formats a date to a string based on the requested format.

date

<td>{{movie.releaseDate | date}}</td>
      
      <td>{{movie.releaseDate | date}}</td>
    

Angular 的 date 管道和它很相似。

The Angular date pipe is similar.

filter

<tr ng-repeat="movie in movieList | filter: {title:listFilter}">
      
      <tr ng-repeat="movie in movieList | filter: {title:listFilter}">
    

根据过滤条件从指定的集合中选取出一个子集。

Selects a subset of items from the defined collection, based on the filter criteria.

没了

none

在 Angular 中,出于性能的考虑,并没有一个类似的管道。 过滤逻辑应该在组件中用代码实现。 如果它将被复用在几个模板中,可以考虑构建一个自定义管道。

For performance reasons, no comparable pipe exists in Angular. Do all your filtering in the component. If you need the same filtering code in several templates, consider building a custom pipe.

json

<pre>{{movie | json}}</pre>
      
      <pre>{{movie | json}}</pre>
    

把一个 JavaScript 对象转换成一个 JSON 字符串。这对调试很有用。

Converts a JavaScript object into a JSON string. This is useful for debugging.

json

<pre>{{movie | json}}</pre>
      
      <pre>{{movie | json}}</pre>
    

Angular 的 json 管道做完全相同的事。

The Angular json pipe does the same thing.

limitTo

<tr ng-repeat="movie in movieList | limitTo:2:0">
      
      <tr ng-repeat="movie in movieList | limitTo:2:0">
    

从集合中选择从(第二参数指定的)起始索引号(0)开始的最多(第一参数指定的)条目数(2)个条目。

Selects up to the first parameter (2) number of items from the collection starting (optionally) at the beginning index (0).

slice

<tr *ngFor="let movie of movies | slice:0:2">
      
      <tr *ngFor="let movie of movies | slice:0:2">
    

SlicePipe 做同样的事,但是两个参数的顺序是相反的,以便于 JavaScript 中的 slice 方法保持一致。 第一个参数是起始索引号,第二个参数是限制的数量。 和 AngularJS 中一样,如果们改用组件中的代码实现此操作,性能将会提升。

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 AngularJS, coding this operation within the component instead could improve performance.

lowercase

<td>{{movie.title | lowercase}}</td>
      
      <td>{{movie.title | lowercase}}</td>
    

把该字符串转成小写形式。

Converts the string to lowercase.

lowercase

<td>{{movie.title | lowercase}}</td>
      
      <td>{{movie.title | lowercase}}</td>
    

Angular 的 lowercase 管道和 1 中的功能完全相同。

The Angular lowercase pipe does the same thing.

number

<td>{{movie.starRating | number}}</td>
      
      <td>{{movie.starRating | number}}</td>
    

把数字格式化为文本。

Formats a number as text.

number

<td>{{movie.starRating | number}}</td> <td>{{movie.starRating | number:'1.1-2'}}</td> <td>{{movie.approvalRating | percent: '1.0-2'}}</td>
      
      <td>{{movie.starRating | number}}</td>
<td>{{movie.starRating | number:'1.1-2'}}</td>
<td>{{movie.approvalRating | percent: '1.0-2'}}</td>
    

Angular 的 number 管道很相似。 但在指定小数点位置时,它提供了更多的功能,如第二个范例所示。

The Angular number pipe is similar. It provides more functionality when defining the decimal places, as shown in the second example above.

Angular 还有一个 percent 管道,它把一个数组格式化为本地化的(local)百分比格式,如第三个范例所示。

Angular also has a percent pipe, which formats a number as a local percentage as shown in the third example.

orderBy

<tr ng-repeat="movie in movieList | orderBy : 'title'">
      
      <tr ng-repeat="movie in movieList | orderBy : 'title'">
    

使用表达式中所指定的方式对集合进行排序。 在这个例子中,movieList 被根据 movie 的 title 排序了。

Displays the collection in the order specified by the expression. In this example, the movie title orders the movieList.

没了

none

在 Angular 中,出于性能的考虑,并没有一个类似的管道。 排序逻辑应该在组件中用代码实现。 如果它将被复用在几个模板中,可以考虑构建一个自定义管道。

For performance reasons, no comparable pipe exists in Angular. Instead, use component code to order or sort results. If you need the same ordering or sorting code in several templates, consider building a custom pipe.

模块/控制器/组件

Modules/controllers/components

无论在 AngularJS 还是 Angular 中,“模块”都会帮你把应用拆分成一些内聚的功能块。

In both AngularJS and Angular, modules help you organize your application into cohesive blocks of functionality.

在 AngularJS 中,你要在控制器中写代码,来为视图提供模型和方法。 在 Angular 中,你要创建组件

In AngularJS, you write the code that provides the model and the methods for the view in a controller. In Angular, you build a component.

因为很多 AngularJS 的代码是用 JavaScript 写的,所以在 AngularJS 列显示的是 JavaScript 代码,而 Angular 列显示的是 TypeScript 代码。

Because much AngularJS code is in JavaScript, JavaScript code is shown in the AngularJS column. The Angular code is shown using TypeScript.

AngularJS

Angular

IIFE

(function () { ... }());
      
      (function () {
  ...
}());
    

在 AngularJS 中,用立即调用的函数表达式(IIFE)来包裹控制器代码可以让控制器代码不会污染全局命名空间。

In AngularJS, an immediately invoked function expression (or IIFE) around controller code keeps it out of the global namespace.

没了

none

在 Angular 中不用担心这个问题,因为使用 ES 2015 的模块,模块会替你处理命名空间问题。

This is a nonissue in Angular because ES 2015 modules handle the namespacing for you.

要了解关于模块的更多信息,参见架构概览中的模块部分。

For more information on modules, see the Modules section of the Architecture Overview.

Angular 模块

Angular modules

angular.module("movieHunter", ["ngRoute"]);
      
      angular.module("movieHunter", ["ngRoute"]);
    

在 AngularJS 中,Angular 模块用来对控制器、服务和其它代码进行跟踪。第二个参数定义该模块依赖的其它模块列表。

In AngularJS, an Angular module keeps track of controllers, services, and other code. The second argument defines the list of other modules that this module depends upon.

NgModules

import { NgModule } from '@angular/core'; import { BrowserModule } from '@angular/platform-browser'; import { AppComponent } from './app.component'; @NgModule({ imports: [ BrowserModule ], declarations: [ AppComponent ], bootstrap: [ AppComponent ] }) export class AppModule { }
      
      import { NgModule }      from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';

import { AppComponent }  from './app.component';

@NgModule({
  imports: [ BrowserModule ],
  declarations: [ AppComponent ],
  bootstrap: [ AppComponent ]
})
export class AppModule { }
    

Angular 的模块用 NgModule 装饰器进行定义,有如下用途:

NgModules, defined with the NgModule decorator, serve the same purpose:

imports: 指定当前模块依赖的其它模块列表

* imports: specifies the list of other modules that this module depends upon

declaration: 用于记录组件、管道和指令。

* declaration: keeps track of your components, pipes, and directives.

要了解关于模块的更多知识,参见NgModules

For more information on modules, see NgModules.

控制器注册

Controller registration

angular .module("movieHunter") .controller("MovieListCtrl", ["movieService", MovieListCtrl]);
      
      angular
  .module("movieHunter")
  .controller("MovieListCtrl",
              ["movieService",
               MovieListCtrl]);
    

在 AngularJS 中,在每个控制器中都有一些代码,用于找到合适的 Angular 模块并把该控制器注册进去。

AngularJS has code in each controller that looks up an appropriate Angular module and registers the controller with that module.

第一个参数是控制器的名称,第二个参数定义了所有将注入到该控制器的依赖的字符串名称,以及一个到控制器函数的引用。

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.

组件装饰器

Component decorator

@Component({ selector: 'app-movie-list', templateUrl: './movie-list.component.html', styleUrls: [ './movie-list.component.css' ], })
      
      @Component({
  selector: 'app-movie-list',
  templateUrl: './movie-list.component.html',
  styleUrls: [ './movie-list.component.css' ],
})
    

Angular 会往组件类上添加了一个装饰器,以提供所需的任何元数据。 @Component 装饰器把该类声明为组件,并提供了关于该组件的元数据,比如它的选择器(或标签)和模板。

Angular adds 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.

这就是把模板关联到代码的方式,它定义在组件类中。

This is how you associate a template with logic, which is defined in the component class.

要了解关于组件的更多信息,参见架构概览中的组件部分。

For more information, see the Components section of the Architecture Overview page.

控制器函数

Controller function

function MovieListCtrl(movieService) { }
      
      function MovieListCtrl(movieService) {
}
    

在 AngularJS 中,你在控制器函数中编写模型和方法的代码。

In AngularJS, you write the code for the model and methods in a controller function.

组件类

Component class

export class MovieListComponent { }
      
      export class MovieListComponent {
}
    

在 Angular 中,你将创建一个组件类来容纳数据模型和控制方法。使用 TypeScript 的 export 关键字导出该类,以便可以将此功能导入 NgModules 中。

In Angular, you create a component class to contain the data model and control methods. Use the TypeScript export keyword to export the class so that the functionality can be imported into NgModules.

要了解关于组件的更多信息,参见架构概览中的组件部分。

For more information, see the Components section of the Architecture Overview page.

依赖注入

Dependency injection

MovieListCtrl.$inject = ['MovieService']; function MovieListCtrl(movieService) { }
      
      MovieListCtrl.$inject = ['MovieService'];
function MovieListCtrl(movieService) {
}
    

在 AngularJS 中,你把所有依赖都作为控制器函数的参数。 这个例子注入了一个 MovieService

In AngularJS, you pass in any dependencies as controller function arguments. This example injects a MovieService.

为了防止在最小化时出现问题,第一个参数明确告诉 Angular 它应该注入一个 MovieService 的实例。

To guard against minification problems, tell Angular explicitly that it should inject an instance of the MovieService in the first parameter.

依赖注入

Dependency injection

constructor(movieService: MovieService) { }
      
      constructor(movieService: MovieService) {
}
    

在 Angular 中,你要把依赖作为组件构造函数的参数传入。 这个例子注入了一个 MovieService。 即使在最小化之后,第一个参数的 TypeScript 类型也会告诉 Angular 它该注入什么。

In Angular, you pass in dependencies as arguments to the component class constructor. This example injects a MovieService. The first parameter's TypeScript type tells Angular what to inject, even after minification.

要了解关于依赖注入的更多信息,参见架构概览中的依赖注入部分。

For more information, see the Dependency injection section of the Architecture Overview.

样式表

Style sheets

样式表让你的应用程序看起来更漂亮。 在 AngularJS 中,你要为整个应用程序指定样式表。 随着应用程序的不断成长,为各个部分指定的样式会被合并,导致无法预计的后果。 在 Angular 中,你仍然要为整个应用程序定义样式,不过现在也可以把样式表封装在特定的组件中。

Style sheets give your application a nice look. In AngularJS, you specify the style sheets for your entire application. As the application grows over time, the styles for the many parts of the application merge, which can cause unexpected results. In Angular, you can still define style sheets for your entire application. But now you can also encapsulate a style sheet within a specific component.

AngularJS

Angular

<link href="styles.css" rel="stylesheet" />
      
      <link href="styles.css" rel="stylesheet" />
    

AngularJS 在 index.htmlhead 区使用 link 标签来为应用程序定义样式。

AngularJS, uses a link tag in the head section of the index.html file to define the styles for the application.

样式配置

Styles configuration

"styles": [ "styles.css" ],
      
      "styles": [
  "styles.css"
],
    

使用 Angular CLI,你可以在 angular.json 文件中配置全局样式。 也可以把扩展名改为 .scss 来使用 sass。

With the Angular CLI, you can configure your global styles in the angular.json file. You can rename the extension to .scss to use sass.

StyleUrls

在 Angular 中,你可以在 @Component 的元数据中使用 stylesstyleUrls 属性来为一个特定的组件定义样式表。

In Angular, you can use the styles or styleUrls property of the @Component metadata to define a style sheet for a particular component.

styleUrls: [ './movie-list.component.css' ],
      
      styleUrls: [ './movie-list.component.css' ],
    

这让你可以为各个组件设置合适的样式,而不用担心它泄漏到程序中的其它部分。

This allows you to set appropriate styles for individual components that won’t leak into other parts of the application.