<body>
<div id='root'></div>
<script src="./react.js"></script>
<script src="./react-dom.js"></script>
<script src="./babel.min.js"></script>
<script type="text/babel">
var arr=['111','222','333']
//只给第一项加active 如果多项要active 可以用插件,后面讲
ReactDOM.render((
<ul>
{arr.map((val,index)=>{
return (<li key={index} className={index==0?'active':''}>{index}---{val}</li>)
})
}
</ul>
),document.getElementById('root'))
</script>