refactor

# Refactor ## Overview Improve code structure and readability without changing external behavior. Refactoring is gradual evolution, not revolution. Use this for improving existing code, not rewriting from scratch. ## When to Use Use this skill when: - Code is hard to understand or maintain - Functions/classes are too large - Code smells need addressing - Adding features is difficult due to code structure - User asks "clean up this code", "refactor this", "improve this" --- ## Refactoring Principles ### The Golden Rules 1. **Behavior is preserved** - Refactoring doesn't change what the code does, only how 2. **Small steps** - Make tiny changes, test after each 3. **Version control is your friend** - Commit before and after each safe state 4. **Tests are essential** - Without tests, you're not refactoring, you're editing 5. **One thing at a time** - Don't mix refactoring with feature changes ### When NOT to Refactor ``` - Code that works and won't change again (if it ain't broke...) - Critical production code without tests (add tests first) - When you're under a tight deadline - "Just because" - need a clear purpose ``` --- ## Common Code Smells & Fixes ### 1. Long Method/Function ```diff # BAD: 200-line function that does everything - async function processOrder(orderId) { - // 50 lines: fetch order - // 30 lines: validate order - // 40 lines: calculate pricing - // 30 lines: update inventory - // 20 lines: create shipment - // 30 lines: send notific...