@description



Angular applications are made up of _components_.
  A _component_ is the combination of an HTML template and a component class that controls a portion of the screen. Here is an example of a component that displays a simple string:
  
Angular 应用是由*组件*组成的。
  *组件*由 HTML 模板和组件类组成，组件类控制视图。下面是一个显示简单字符串的组件:


<code-example path="quickstart/src/app/app.component.ts" title="src/app/app.component.ts" linenums="false">

</code-example>




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Try this **<live-example noDownload>QuickStart example on Plunker</live-example>** without installing anything.
Try it locally with the [***QuickStart seed***](guide/guide/setup "Setup for local development with the QuickStart seed")
and prepare for development of a real Angular application.

试试这个**<live-example noDownload>Plunker上的QuickStart范例</live-example>**。
也可以在本地使用[***QuickStart种子工程***](guide/guide/setup "Setup for local development with the QuickStart seed")来为开发真实的Angular应用做好准备。


</div>



Every component begins with an `@Component` [decorator](guide/glossary#decorator '"decorator" explained')
function that takes a _metadata_ object. The metadata object describes how the HTML template and component class work together.

每个组件都以`@Component`[装饰器](guide/glossary#!{_decorator} '"!{_decorator}" explained')函数开始，它接受一个_元数据_对象参数。该元素对象描述了 HTML 模板和组件类是如何一起工作的。

The `selector` property tells Angular to display the component inside a custom `<my-app>` tag in the `index.html`.

`selector`属性为 Angular 指定了在`index.html`中的自定义`<my-app>`标签里显示该组件。


<code-example path="quickstart/src/index.html" region="my-app" title="index.html (inside &lt;body&gt;)" linenums="false">

</code-example>



The `template` property defines a message inside an `<h1>` header.
The message starts with "Hello" and ends with `{{name}}`,
which is an Angular [interpolation binding](guide/guide/displaying-data) expression.
At runtime, Angular replaces `{{name}}` with the value of the component's `name` property. 
Interpolation binding is one of many Angular features you'll discover in this documentation.

`template`属性定义了`<h1>`标题里的一条消息。
该消息以 “Hello” 开始，以 Angular [插值绑定](guide/guide/displaying-data)表达式`{{name}}`结束。
在运行时，Angular 用组件的`name`属性值替换`{{name}}`。
插值绑定是 Angular 的特征之一。你将在本文档中探索更多 Angular 的特征。


In the example, change the component class's `name` property from `'Angular'` to `'World'` and see what happens.

在这个例子中，把组件类的`name`属性从`'Angular'`改为`'World'`，看看会怎么样。


<div class="callout is-helpful">



<header>
  A word about TypeScript
</header>



<header>
  关于 TypeScript
</header>



<p>
  This example is written in <a href="http://www.typescriptlang.org/" target="_blank" title="TypeScript">TypeScript</a>, a superset of JavaScript. Angular
  uses TypeScript because its types make it easy to support developer productivity with tooling. You can also write Angular code in JavaScript; <a href="cookbook/ts-to-js.html">this guide</a> explains how.

</p>



<p>
  本例是用 JavaScript 的一个超集 <a href="http://www.typescriptlang.org/" target="_blank" title="TypeScript">TypeScript</a> 编写的。
  Angular 使用 TypeScript 是因为它的类型可以帮助工具提高开发者效率。你也可以用 JavaScript 编写 Angular 代码，参见<a href="cookbook/ts-to-js.html">本指南</a>。

</p>



</div>



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### Next step
    
### 下一步

Start [**learning Angular**](guide/guide/learning-angular "Learning Angular").
    
开始[**学习 Angular**](guide/guide/learning-angular "学习 Angular").

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