Untitled

<html>
    <head>
        <meta charset="UTF-8" />
        <script crossorigin src="https://unpkg.com/react@16/umd/react.production.min.js"></script>
        <script crossorigin src="https://unpkg.com/react-dom@16/umd/react-dom.production.min.js"></script>
        <script>
            ReactDOM.render(<h1>Hello, world!</h1>,document.getElementById('root'));

        </script>
    </head>
    <body>
        <div id="root"></div>
    </body>
</html>