How to make a client for a site that handles logins with Facebook?

I'm writing a client in NodeJS that is meant to replace using a website, and it isn't my website. It uses Facebook to log in. Is it possible to log in via a Facebook username/password? It seems modules like passport-facebook are intended for use with a website that you own, which is not the case in my scenario.

I suspect that I can't login with a username and password, so I'd have to sniff web traffic of me browsing the normal website for my token for the website, and then somehow use that in Node, but I hope this isn't the case.

Thanks for your help.

via Ashley Herald