70 lines
2.3 KiB
HTML
70 lines
2.3 KiB
HTML
<!--
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* @Author: chenxuan
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* @Date: 2022-01-13 22:59:55
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* @LastEditTime: 2022-01-13 23:14:43
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* @LastEditors: chenxuan
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-->
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<meta http-equiv="X-UA-Compatible" content="IE=edge">
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<meta name="viewport" content="width=device-width, initial-scale=1.0">
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<title>getSnapshotBeforeUpdate</title>
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<script src="../package/new/react.development.js"></script>
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<script src="../package/new/react-dom.development.js"></script>
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<script src="../package/new/babel.min.js"></script>
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</head>
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<body>
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<div id="app"></div>
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<script type="text/babel">
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class Count extends React.Component{
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constructor(props){
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console.log("1-constructor")
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super(props)
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this.state={count:100}
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}
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add=()=>{
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let {count}=this.state;
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count+=1;
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this.setState({count})
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}
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render(){
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console.log("3-render")
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return (
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<div>
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<h2>当前求和为：{this.state.count}</h2>
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<button onClick={this.add}>点我+1</button>
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</div>
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)
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}
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componentDidMount(){
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console.log('4-componentDidMount')
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}
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componentWillUnmount(){
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console.log("5-componentWillUnmount")
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}
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// 控制组件更新的阀门
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shouldComponentUpdate(){
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console.log('shouldComponentUpdate')
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return true
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}
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// 组件更新之前搞一些事情
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// 次钩子函数的任何值都会传递给componentDidUpdate
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getSnapshotBeforeUpdate(prevProps,prevState){
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// console.log(preState)
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return "getSnapshotBeforeUpdate"
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}
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componentDidUpdate(preProps,preState,snapshotValue){
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console.log(snapshotValue)
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// console.log(preProps,preState)
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// console.log('componentDidUpdate')
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}
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}
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ReactDOM.render(
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<Count count={1999} />,document.getElementById('app')
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)
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</script>
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</body>
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</html> |