How to track Member logins with GA4

Hello,

I am trying to track member logins in GA4. I have all other tracking set up except member logins. Here is javascript code for this:

dataLayer.push({
  'userId': {{ member_id }}
});

I need to get and pass the member ID.

1) How can I get the Member ID upon login using javascript?

2) How can I get the Member ID when members access any page in the members' area?

Thank you,

C

Is this not possible? Am I approaching this the wrong way? Any help is appreciated.