Refactoring Legacy Code: The Jedi Move of Extracting Pure Functions (opens in new tab)

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? I opened the file and found a 200‑line monster called calculateOrderTotal. Inside, there were nested if statements that checked user type, coupon validity, tax rules, and even a weird side‑effect that w...