React State状态与生命周期的实现方法

<div id="app"></div>
<script type="text/babel">
  var ReactDiv = document.getElementById('app');
  function GetReactComp(){
    return <p>我是react组件</p>
  }
  const hellocomp = < GetReactComp />  //首字母大写
  const reactSpan = (
    <span>
      { hellocomp }
    </span>
  )
  ReactDOM.render(reactSpan,ReactDiv)
</script>

<div id="class"></div>
<script type="text/babel">
  var reactDiv1=document.getElementById('class');
  //定义类组件
  class MyReactComp extends React.Component{
    render(){
      return (
        <h2>类组件</h2>
      )
    }
  }
  //使用类组件
  const testDiv = (
    <div>{<MyReactComp/>}</div>
  )
	//挂载
  ReactDOM.render(testDiv,reactDiv1)
</script>

<div id="app"></div>
<script type="text/babel">
  var reactDiv = document.getElementById('app');
  class ReactClassComp extends React.Component {
    render(){
      return (
      <div>
      <p>用户名：<input type="text" value={ this.props.name }/></p>
      <p>性别：<input type="text" value={ this.props.gender }/></p>
      </div>
      )
    }
  }

  ReactClassComp.defaultProps={
    name:'刘备',
    gender:'男'
  }
  const reactp=(
    <span>
      {<ReactClassComp />}  
    </span>
  )
  ReactDOM.render(reactp,reactDiv)
</script>

constructor(props){
	super(props)；
		this.state = {
			date:new Date()
		}
		this.handleShow = this.handleShow.bind(this)
	
}

compomentDidUpdate(prevProps){
	if(this.props.userID !== prevProps.userID){
		this.fetchData(this.props.userID)
	}
}

<div id="app"></div>
<script type="text/babel">
  var reactDiv = document.getElementById('app')
  //定义类组件 MyStateComp 
  class MyStateComp extends React.Component {
    //构造函数
    constructor(props) {
      super(props); 
      //通过this.state初始化state内部
      this.state = {
        date:new Date(),
        show:false,
        text:'显示'
      }
      //为事件处理函数绑定实例
      this.handleShow = this.handleShow.bind(this)
    }
    //添加订阅
    componentDidMount() {
      this.timerID = setInterval(()=>this.tick(),1000)
    }
    //时间函数
    tick() {
      this.setState({  //setState更新组件的state
        date:new Date()
      })
    }
    //实例显示、隐藏
    handleShow() {
      this.setState(state=>({
        show: !state.show,
        text: !state.show?'隐藏':'显示'
      }))
    }
    //组件卸载：清空定时器
    componentWillUnmont() {
      clearInterval(this.timerID)
    }
    
    render() {
      let isShow=this.state.show;
      let element;
      if(isShow){
        element = <h2 >{this.state.date.toLocaleTimeString()}</h2> 
      }else{
        element = null
      }
      return (
        <div>
          <button onClick={this.handleShow}>{this.state.text}时间</button>
          {element}
        </div>
      )
    }
  }
  const reactSpan = (
    <span>
      {<MyStateComp/> }  
    </span>
  )
  ReactDOM.render(reactSpan,reactDiv)
</script>