W3Schools Tryit Editor

main.jsx

index.html

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

//Check out the index.html file, were we have added some styles.

function Car() {
  const x = "myclass";
  return (
    <h1 className={x}>Hello World</h1>
  );
}

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

<!DOCTYPE html>
<html lang="en">
  <!--This is not how we should add styles in React,
  but for demo purposes, it is ok: -->
  <style>
    .myclass {
      color: red;
    }
  </style>
  <body>
    <div id="root"></div>
    <script type="module" src="/src/main.jsx"></script>
  </body>
</html>