that the image what is going on when i run the react file> this is my app.js file

I m trying to create an app every time I got a page unresponsive in my browser

    import './App.css';

function App() {
  return (
    <div className="App">
    <h1>Hiii</h1>
    </div>
  );
}

export default App;                                                     

                                                
                                                                                

this is the index.js file

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


ReactDOM.render(
  <React.StrictMode>
    <App />
  </React.StrictMode>,
  document.getElementById('root')
);