The fetch function does not send cookies by default. There are two possible ways to send cookies:

1. Only send cookies if the URL is on the same origin as the calling script.

   fetch('/login', {
       credentials: 'same-origin'
   })
   

2. Always send cookies, even for cross-origin calls.

   fetch('<https://otherdomain.com/login>', {
       credentials: 'include'
   })