The Refactor Awakens: A Practical Guide to Pure Functions

Short summary

A practical guide to refactoring side-effect-heavy legacy code using pure functions. The author walks through a real-world processOrder function that mutates inputs and calls four external services, showing how extracting pure data-transformation helpers makes code testable, reusable, and safer to change. Side effects get pushed to the edges while orchestration stays thin.

• •Pure functions: same inputs always yield same outputs, no side effects
• •Extracting pure helpers from monolithic functions makes them independently testable
• •Push side effects to the edges; keep orchestration thin and readable
• •Side effects are the root cause of most flaky tests and refactor anxiety

Generated with AI, which can make mistakes.