index.js

const App = () => {
  const [resource, setResource] = useState(initialResource);
  const [startTransition, isPending] = useTransition({timeoutMs: 1000});
  return (
    <>
      <button 
        disabled={isPending}
        onClick={() => {
          startTransition(() => {
            setResource(carResource);
          });
        }}
      >Load cars</button>
      {isPending ? "Loading..." : null}
      <CarView resource={resource}/>
    </>
  );
}