编程教程示范演示-小库网

小库网 React 实例</title>
<script src="https://lf26-cdn-tos.bytecdntp.com/cdn/expire-1-M/react/18.2.0/umd/react.production.min.js" ></script>
<script src="https://lf3-cdn-tos.bytecdntp.com/cdn/expire-1-M/react-dom/18.2.0/umd/react-dom.production.min.js"></script>
<script src="https://lf9-cdn-tos.bytecdntp.com/cdn/expire-1-M/babel-standalone/6.26.0/babel.min.js" ></script>

<div id="root"></div>
<script type="text/babel">
class Header extends React.Component {
  constructor(props) {
    super(props);
    this.state = {favoritesite: "runoob"};
  }
  componentDidMount() {
    setTimeout(() => {
      this.setState({favoritesite: "google"})
    }, 1000)
  }
  getSnapshotBeforeUpdate(prevProps, prevState) {
    document.getElementById("div1").innerHTML =
    "在更新前喜欢的网站是：" + prevState.favoritesite;
  }
  componentDidUpdate() {
    document.getElementById("div2").innerHTML =
    "更新后喜欢的网站是：" + this.state.favoritesite;
  }
  render() {
    return (
      <div>
        <h1>我喜欢的网站是 {this.state.favoritesite}</h1>
        <div id="div1"></div>
        <div id="div2"></div>
      </div>
    );
  }
}
 
const root = ReactDOM.createRoot(document.getElementById("root"));
root.render(<Header />);
</script>