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:
src/app/app.component.ts
Try this
试试这个
Every component begins with an @Component decorator
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。
index.html (inside <body>)
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 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。
This example is written in TypeScript, 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; this guide explains how.
本例是用 JavaScript 的一个超集 TypeScript 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，参见本指南。