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

1. Identify code smell
2. Write characterization tests if missing
3. Apply refactoring
4. Run tests
5. Commit
6. Repeat

Code Smells to Watch

• Long methods (>20 lines)
• Long parameter lists (>3 params)
• Duplicate code
• Feature envy
• Data clumps
• Primitive obsession