# Refactoring

> Safe code refactoring with step-by-step approach

- Skill: `majiayu000/refactoring-9` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds add majiayu000/refactoring-9`
- Raw SKILL.md: https://api.skillmd.com/api/skills/majiayu000/refactoring-9/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: majiayu000 (https://skillmd.com/u/majiayu000)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/majiayu000/refactoring-9

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# 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