How nginx proxy redirects websites between multiple domain names

Question

There is such a website. The login interface is domain name A. After successful login, it will jump to another domain name B.
If you directly access the B domain name, it will jump to the A domain name without logging in. If you have already logged in, you are still in domain name B.

Answer 1

It is recommended not to use Nginx configuration, it will be better to implement it on the front end

Answer 2

Use business code to implement it to determine whether you are logged in. If you are not logged in, initiate a redirect. It is a very mature solution.