title: Firebase authentication using NodeJS
body: <p>So far I was working with Mongodb and Express. There my whole authentication was done by checking <code>req.user</code> object. From what I saw, Firebase authentication is mostly done in the front end. How can I get <code>req.user</code> to work with Firebase in the back end? I saw a couple of <a href="https://youtu.be/KdLDIob_WDM?list=PLJm7_t7JnSjn__VC3sK86o2YlUuwlPKkO" rel="noreferrer">tutorials</a>, but they just showed a couple of methods and went on. I mean to ask more about the logic, but some code examples would probably help.</p>