For Future Reference

I had the following code in my front-end app:

  const result = await fetch(url, {
    method: 'patch',
    headers: {
      'Content-Type': 'application/json'
    },
    body: json,
    mode: 'cors'
  });

I was getting CORS errors but I could see that the OPTIONS request was sending back PATCH as an allowed method. After banging my head against a wall for at least 2 hours, I finally stumbled on this StackOverflow post. BOOM! Problem solved! "patch" needed to be "PATCH".

Hope this helps someone!