4.生命周期.html

<!doctype html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport"
          content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <script src="node_modules/react/dist/react.js"></script>
    <script src="node_modules/react-dom/dist/react-dom.js"></script>

</head>
<!--jsx-->
<body>
<div id="root">

</div>
<script src="node_modules/babel-standalone/babel.js"></script>
<!--jsx  基类  父类 顶层类  -->
<script type="text/babel">
    class Time extends React.Component{
        constructor(){
            super();
            this.state={time:0};
            console.log("构造函数");
        }
       /*组件即将装配到页面当中   一个组件从无到有的过程*/
        componentWillMount(){
          console.log("组件即将装配到页面当中")
        }

        render(){
            console.log("组件正在装配到页面当中")
            return <div>{this.state.time}</div>
        }
        /*组件已经渲染到页面当中*/
        componentDidMount(){
            var num=0;
            setInterval(()=>{
                console.log(num);
                num++
                this.setState({time:num})
            },1000)
        }
    }

    ReactDOM.render(<Time/>,document.getElementById("root"))
</script>
</body>
</html>