CORS error in Next JS

[yogthesharma]

I have developed a simple e-commerce website using next js , it is working fine on my machine but after deploying it to vercel on every request made to backend it throws a "Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://localhost:3000/api/userAuth. (Reason: CORS request did not _succeed)." error as also shown in picture. Here is the code from my backend where i tried to resolve my issue.