How to get user info on a static page?

I'm hosting a static page/site on GCP App Engine (written in standard js/html/css), on a company domain ;

I know in localhost testing I can't get the user info in any way (which is fine, I'll hardcode dummy data).

But after using gcloud app deploy and running it on the engine, is there a way to obtain user info somehow? Name, email etc. Ideally just through the app somehow - or even by calling a google cloud function or something.

Nb. I have activated IAP so when hosted, the user does go through google auth on this site (all domain users are allowed in).