https://medium.freecodecamp.org/learn-how-to-handle-authentication-with-node-using-passport-js-4a56ed18e81e

In this article you will learn how to handle authentication for your Node server using Passport.js. This article does not cover Frontend authentication. Use this to configure your Backend authentication (Generate token for each user & protect routes).

Keep in mind that if you get stuck on any step, you can refer to this GitHub repo.