refactor

name	refactor
description	Surgical code refactoring to improve maintainability without changing behavior. Use for gradual improvements: extract functions, eliminate code smells, improve type safety, apply design patterns.

When to Use

• Code is hard to understand or maintain
• Functions/classes are too large (> 50 lines)
• Duplicated logic across multiple files
• Adding features is difficult due to code structure
• User asks "clean up this code", "refactor this", "improve this"

Golden Rules

1. Behavior is preserved — refactoring doesn't change what the code does, only how
2. Small steps — make one change at a time, run tests after each
3. Tests first — without tests, you're not refactoring, you're editing
4. One thing at a time — don't mix refactoring with feature changes

Common Code Smells to Fix

Smell	Fix
Long function (> 50 lines)	Extract smaller functions
Duplicated code	Extract shared utility/helper
Large class/component	Split by single responsibility
Long parameter list	Group into interface/object
Nested conditionals (arrow code)	Use guard clauses / early returns
Magic numbers/strings	Extract named constants
Dead code	Delete it (git history preserves it)
No type safety	Add TypeScript interfaces and types

Refactoring Process

1. PREPARE   — ensure tests exist, commit current state
2. IDENTIFY  — find the smell, understand what the code does
3. REFACTOR  — one small change, run tests, commit if passing
4. VERIFY    — all tests pass, behavior unchanged
5. CLEAN UP  — update comments, final commit

Checklist

• Functions are small and do one thing
• No duplicated logic
• Descriptive names (variables, functions, components)
• No magic numbers/strings
• Dead code removed
• Types defined for all public APIs
• No any types without justification
• All tests still pass

Source: github/awesome-copilot — refactor