Ask HN: (Anyone has written / Hot to write) a functional codebase?

Hi Everyone, I am a developer with 2 years of experience in Angular. When I started working I have no idea about OOPS, Functional Programming or Reactive Programming. But as Angular is tightly coupled with RXJS, I get to learn about reactive programming. Initially, I was not adhering to the programming paradigm and was writing kind of spaghetti code. But slowly after watching lots of conference videos, and lots of reading, I get to hold on Reactive Programming and the quote "Everything is a stream" started making sense to me, now I am pretty comfortable in writing almost all my code in Observable and Subjects.

While transitioning to this period I also get to know about what is functional programming and writing pure Observable streams. I understand functional programming up to this mark only.

- Pure Functions - Dot Chaining

That's it. I want to learn more of this stuff but I don't know how to start writing pure code. What to do about state change and side effects. I wanted to learn by taking a look at other people code and if anyone has a better suggestion do let me know.

These are the resources I am already aware of and reading right now.

- Composing Software by Erir Elliott - Mostly Adequate Guide by Dr. Frisby

The thing with books is that they only explain you the concept but it's hard for me to get ideas from the book and directly applying them in the codebase I am writing or in the job. Please reach out to me, if you can teach me something or provide any guidance.