Q:

User functionality in Backbone.js Node.js Express.js

I'm making a webapp using Backbone.js, Node.js, and Express.js and want to
add User functionality (login, logout, profiles, displaying content
relevant to that user). I'm planning on using Passport to do the signing in
and out. I'm confused though about how the frontend knows which user is 
logged in for the rest of the session. Do I need to have some variable in the 
Backbone Router called "loggedInUser" that points to a User model?
Or is it the server that needs to know this information and I need to have 
the variable somewhere on the server? In other words, where should I store 
the logged in user's info so that I can make requests and responses relevant 
to the currently logged in user and display information relevant to them? Hopefully my wording is clear. Also, if anyone could 
provide links to helpful articles on this, that would be great too! Thank 
you!

A:

Passport already helps you do this. Use passport sessions. The currently logged in user is already available on the server as req.user on every request and the client knows the session information via the session cookies which are handled by passport. 

