The Quest Begins (The “Why”)
Picture this: I’m deep in a codebase that looks like the junkyard planet from Star Wars—tangled wires, rusted droids, and a mysterious hum coming from somewhere I can’t quite locate. My task? Add a simple discount rule to an e‑commerce checkout. Sounds easy, right?
That moment hit me like Neo seeing the Matrix for the first time: if I could isolate the pure calculations, the rest would become trivial. I needed a lightsaber, not a sledgehammer.
The Revelation (The Insight)
The treasure I uncovered? Extracting pure functions—small, deterministic pieces that take inputs, return outputs, and never touch the outside world. A pure function is like a Jedi’s lightsaber swing: predictable, repeatable, and free of side‑effects. When you isolate the “what” (the calculation) from the “how” (state changes, I/O, logging), you gain:
