菜鸟教程在线编辑器

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<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>菜鸟教程 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>
</head>
<body>
<div id="root"></div>
<script type="text/babel">
class Header extends React.Component {
  constructor(props) {
    super(props);
    this.state = {favoritesite: "runoob"};
  }

shouldComponentUpdate() {
    return true; // 修改此处以允许组件更新
  }

changeSite = () => {
    this.setState({favoritesite: "google"});
  }

render() {
    return (
      <div>
        <h1>我喜欢的网站是 {this.state.favoritesite}</h1>
        <button type="button" onClick={this.changeSite}>修改</button>
      </div>
    );
  }
}

const root = ReactDOM.createRoot(document.getElementById("root"));
root.render(<Header />);
</script>

</body>
</html>

​x
 
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8" />
<title>菜鸟教程 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>
</head>
<body>
<div id="root"></div>
<script type="text/babel">
class Header extends React.Component {
  constructor(props) {