How to roll your own auth in JavaScript & TypeScript

Authentication is an important topic of any application. It's the gatekeeper that ensures only the right people can access the right resources. But how do you roll your own authentication in JavaScript & TypeScript? In this tutorial, we'll explore how to build a session-based authentication system. The motivation behind this tutorial is the deprecation on Lucia. I've been using Lucia before, it was a great library, but the author decided to transform it into a learning resource. So whenever something is unclear in this tutorial, you can refer to the official resource, because I just try to distill the essence of it into a step by step guide.