A very bare bones React app that simply tries to hit some endpoint.
Simply go to the src/App.tsx file and near the top of the file, set these constants with the appropriate values, or modify the request so it doesn't:
const url = ''; // your url
const bearerToken = undefined; // your bearer token, if neededThen just run yarn start and it will open a browser and explode or not explode telling you if you have, in fact, fixed your CORs issues.
Cheers.