# Canvas

Canvas是HTML5新增的组件，它就像一块幕布，可以用JavaScript在上面绘制各种图表、动画等。

没有Canvas的年代，绘图只能借助Flash插件实现，页面不得不用JavaScript和Flash进行交互。有了Canvas，我们就再也不需要Flash了，直接使用JavaScript完成绘制。

一个Canvas定义了一个指定尺寸的矩形框，在这个范围内我们可以随意绘制：

```html
<canvas id="test-canvas" width="300" height="200"></canvas>
```

由于浏览器对HTML5标准支持不一致，所以，通常在`<canvas>`内部添加一些说明性HTML代码，如果浏览器支持Canvas，它将忽略`<canvas>`内部的HTML，如果浏览器不支持Canvas，它将显示`<canvas>`内部的HTML

```html
<canvas><p>浏览器不支持canvas组件</p></canvas>
```




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