02_Hello_React案例

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>

    <div id="root"></div>
    
     <!-- 引入依赖 -->
     <script crossorigin src="https://unpkg.com/react@18/umd/react.development.js"></script>
     <script crossorigin src="https://unpkg.com/react-dom@18/umd/react-dom.development.js"></script> 
     <script src="https://unpkg.com/babel-standalone@6/babel.min.js"></script>
    
    <!-- 编写React代码 -->
    <script type="text/babel">

        const root = ReactDOM.createRoot(document.querySelector("#root"));
       
        //1.将文本定义成变量
        let message = "Hello World"

        //2.监听按钮的点击
        function btnClick(){
           
            //1.1修改数据
            message = "Hello React"

            // 2.重新渲染界面
            
            rootRender()
        }
       
        //3.封装一个渲染函数
        function rootRender(){
            root.render((
            <div>
                <h2>{message}</h2>
                <button onClick={btnClick}>修改文本</button>    
            </div>
            ))
        }

        rootRender()
    </script>

</body>
</html>