在ReactDOM.render里面我们写我们的自定义组件的时候有时需要加一下子元素进去：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<body>
<div id="app"></div>
<script src="common/react.js"></script>
<script src="common/react-dom.js"></script>
<script src="https://cdn.bootcss.com/babel-core/5.8.38/browser.js"></script>
<script type="text/babel">
class App extends React.Component {
render() {
return <div>
{/*props.children获取下面4个子节点:3个元素节点和1个文字节点*/}
{this.props.children.map((item,index)=> <p key={index}>{item}</p>)}
</div>
}
}
ReactDOM.render(
<App>
{/*加一些子元素*/}
<span>rick</span>
<span>zhangamie</span>
<span>react</span>
2132132
</App>,
document.getElementById('app')
)
</script>
</body>
</html>