useeffect not rendering react code example

Example 1: react useeffect on change props

useEffect(() => console.log('value changed!'), [props.isOpen]);

Example 2: useeffect cleanup function

function App() {
  const [shouldRender, setShouldRender] = useState(true);

  useEffect(() => {
    setTimeout(() => {
      setShouldRender(false);
    }, 5000);
  }, []);

  // don't render
  if( !shouldRender ) return null;
  // JSX, if the shouldRender is true
  return <ForExample />;
}