helloworld.html

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div id="root"></div>

    <script src="https://unpkg.com/@babel/standalone/babel.js"></script>
    <script type="importmap">
        {
            "imports": {
                "react": "https://esm.sh/react?dev",
                "react-dom/client": "https://esm.sh/react-dom/client?dev"
            }
        }
    </script>

    <script type="text/babel" data-type="module">
        import React, { StrictMode } from 'react'
     
        import { createRoot } from 'react-dom/client'

        function App() {
            return <h1>Hello, World!</h1>
        }

        const root = createRoot(document.getElementById('root'))
        root.render(<StrictMode><App /></StrictMode>)
    </script>
</body>

</html>