Running client-side code after sign-in

[enesse]

I need to perform some client-side operations after a user has signed in for the first time (but not necessary a new user) , like fetching favourite items from an external API and adding them local storage etc. I thought about redirecting the users to a specific page (after sign-in) where I could run my code, but I really don't want to interrupt the user experience by not redirecting them back to where they came from before signing in. One solution could might be a new status that could be signed-in, which we could check similar to authenticated, unauthenticated, loading, but I really don't know.. how do you recommend doing something like this?