W3Schools Tryit Editor

main.jsx

index.html

import { createRoot } from 'react-dom/client';

const Header = () => {
  return (
    <>
      <h1 style={{color: "red"}}>Hello Style!</h1>
      <p>Add a little style!</p>
    </>
  );
}

createRoot(document.getElementById('root')).render(
  <Header />
);

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