javascript Login

Hi to everyone, I have a simple question .
I am writing an application for xerox machine that interface with efi Rip.
Xerox app use Javascript, so i need to write my app in javascript. the only problem is that I've never use javascript so I'd like to know how can I re-write for example the "login" funcion (from nodejs to javascript) so I can start develop my app.
Is there anyone that can tell me how could I do?