ReactSuspenseExample.jsx

import React from 'react';
import ReactDOM from 'react-dom';

let shouldRender = false;
const Children = () => {
    if (shouldRender) {
        return (<div>Hello world</div>);
    }
    throw new Promise((resolve) => {
        setTimeout(() => {
            shouldRender = true;
            resolve();
        }, 2000);
    });
}
  
const App = ({ children }) => (
  <div>
   <h1>Wait for something</h1>
   <React.Suspense fallback={<span>Loading</span>}>
     {children}
   </React.Suspense>
  </div>
);

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