W3Schools Tryit Editor

main.jsx

index.html

import React from 'react';
import ReactDOM from 'react-dom/client';
import './App.css';

class MyHeader extends React.Component {
  render() {
    return (
      <div>
      <h1>Hello Style!</h1>
      <p>Add a little style!.</p>
      </div>
    );
  }
}

const container = document.getElementById('root');
const root = ReactDOM.createRoot(container);
root.render(<MyHeader />);

/*
Notice that you now have three files in your project:
'index.js', 'index.html', and 'App.css'.
*/

<!doctype html>
<html lang="en">
  <body>
    <div id="root"></div>
    <script type="module" src="/src/main.jsx"></script>
  </body>
</html>