TypeScript's unions in React

Check this out:

const [requestStatus, setrequestStatus] = useState<
  'loading' | 'error' | 'success'
>('loading');

const getPosts = () => {
  setrequestStatus('loading');
  fetchPosts(count)
    .then(setQuotes)
    .then(() => {
      setrequestStatus('success');
    })
    .catch(() => setrequestStatus('error'));
};