majiayu000 Refactoring Guide
When to Use
Use this skill when refactoring code or improving code structure.
Refactoring Principles
1. Safety First
- Ensure tests exist before refactoring
- Make small, incremental changes
- Commit after each successful step
- Keep functionality identical
2. Common Refactorings
Extract Method
When: Code block does one thing and can be named
Before: Long method with multiple responsibilities
After: Small methods with clear names
Extract Variable
When: Complex expression needs explanation
Before: if (user.age >= 18 && user.country === 'US' && user.verified)
After: const canPurchase = user.age >= 18 && user.country === 'US' && user.verified;
Replace Conditional with Polymorphism
When: Switch/if statements based on type
Before: switch(type) { case 'A': ... case 'B': ... }
After: type.process() // Each type implements process()
3. Step-by-Step Process
- Identify code smell
- Write characterization tests if missing
- Apply refactoring
- Run tests
- Commit
- Repeat
Code Smells to Watch
- Long methods (>20 lines)
- Long parameter lists (>3 params)
- Duplicate code
- Feature envy
- Data clumps
- Primitive obsession