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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 name="viewport" content="width=device-width, initial-scale=1.0" />
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+ <title>Document</title>
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+
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+ <script src="./babel.min.js"></script>
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+
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+ <script src="./react.development.js"></script>
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+
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+ <script src="./react-dom.development.js"></script>
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+ </head>
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+ <body>
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+ <div id="root"></div>
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+ <script type="text/babel">
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+ let root = ReactDOM.createRoot(document.getElementById("root"));
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+ function App() {
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+ return (
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+ <div>
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+ <h1>Hello, React!</h1>
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+ <Flower num={2} />
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+ </div>
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+ );
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+ }
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+ class Flower extends React.Component {
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+ constructor(props) {
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+ super(props);
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+ // props state 可以改变页面
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+ // props 只读 不修改
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+ // state 可修改
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+ this.state = {
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+ currentTime: new Date(),
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+ count: 0
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+ };
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+ }
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+ // 挂载
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+ componentDidMount() {
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+ console.log("挂载");
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+ console.log(this.props)
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+ this.timer = setInterval(() => {
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+ // currentTime: new Date()
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+ // 在react中 响应式更新状态 唯一方法：调用组件实例的setState方法
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+ // setState方法 在修改状态时候 就是新值 与 旧值合并后在覆盖掉旧状态
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+ // this.setState({
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+ // currentTime: new Date(),
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+ // // count: count + 1
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+ // })
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+ this.setState((state, props) => ({
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+ // console.log(state,props),
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+ currentTime: new Date(),
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+ count: state.count + 1 + props.num
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+ // counter: state.counter + props.increment,
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+ }));
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+ }, 1000);
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+ }
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+ // 更新
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+ componentDidUpdate() {
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+ console.log("更新");
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+
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+ }
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+ // 卸载
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+ componentWillUnmount() {
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+ clearInterval(this.timer);
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+ }
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+ render() {
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+ // this.state.currentTime = 30;
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+ // console.log(this.state.count)
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+ return (
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+ <div>
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+ <h1>React</h1>
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+ <h3>{this.state.count}</h3>
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+ <p>当前时间：{this.state.currentTime.toLocaleString()}</p>
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+ </div>
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+ );
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+ }
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+ }
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+
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+ root.render(<App />);
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+ </script>
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+ </body>
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+</html>
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