Code Refactoring Workflow

Systematically improve code quality while maintaining behavior.

Step 1: Scope Definition

What are we refactoring?

• Single function/method
• Single file/module
• Multiple related files
• Entire subsystem

What's the goal?

• Improve readability
• Reduce duplication (DRY)
• Improve performance
• Better separation of concerns
• Update to modern patterns
• Reduce complexity

Step 2: Safety Net

Before any changes:

1. Verify tests exist - Run existing tests, note coverage
2. Create baseline - Commit or stash current state
3. Document behavior - List what the code currently does

git stash # or commit current work
git checkout -b refactor/[description]

Step 3: Identify Smells

Look for:

• Long methods (>20 lines)
• Deep nesting (>3 levels)
• Duplicate code (copy-paste)
• Long parameter lists (>4 params)
• Feature envy (using other object's data extensively)
• God objects (classes doing too much)
• Primitive obsession (strings/ints instead of types)
• Dead code (unused variables/functions)

Step 4: Plan Refactoring

List specific refactorings to apply:

Smell	Location	Refactoring	Risk
Long method	api.ts:processOrder	Extract Method	Low
Duplication	utils.ts, helpers.ts	Extract & Share	Medium

Step 5: Incremental Changes

For each refactoring:

1. Make ONE change - Single responsibility per commit
2. Run tests - Verify behavior unchanged
3. Commit - Small, atomic commits with clear messages

# After each change:
npm test  # or equivalent
git add -p
git commit -m "refactor(scope): description"

Step 6: Refactoring Catalog

Extract Method

// Before
function process() {
  // 20 lines of validation
  // 20 lines of transformation
  // 20 lines of persistence
}

// After
function process() {
  validate();
  transform();
  persist();
}

Replace Conditional with Polymorphism

// Before
function getPrice(type) {
  if (type === 'A') return priceA();
  if (type === 'B') return priceB();
}

// After
const pricers = { A: priceA, B: priceB };
function getPrice(type) {
  return pricers[type]();
}

Introduce Parameter Object

// Before
function createUser(name, email, age, country, role) {}

// After
function createUser(userDetails: UserDetails) {}

Step 7: Verification

After all refactorings:

1. Run full test suite
2. Manual smoke test critical paths
3. Compare behavior before/after
4. Review diff for unintended changes
5. Check performance hasn't regressed

Output

Provide a refactoring summary:

• Changes made (with commit hashes)
• Metrics improved (complexity, duplication, line count)
• Tests passing confirmation
• Any follow-up recommendations