TypeScript Refactor Skill

Safely refactor TypeScript code with full verification.

Pre-Refactor Checklist

1. Run current tests to establish baseline:

   npm run test

2. Run type check:

   npm run typecheck

3. Note current state as baseline

Refactoring Patterns

Extract Function

// Before
function process(data: Data) {
  // complex validation logic
  if (!data.field1) throw new Error("field1 required");
  if (!data.field2) throw new Error("field2 required");
  // ... more processing
}

// After
function validateData(data: Data): void {
  if (!data.field1) throw new Error("field1 required");
  if (!data.field2) throw new Error("field2 required");
}

function process(data: Data) {
  validateData(data);
  // ... more processing
}

Extract Component (React)

// Before: Large component with repeated patterns
// After: Smaller, focused components with clear props

Rename Symbol

# Find all usages first
grep -r "oldName" --include="*.ts" --include="*.tsx" src/

Post-Refactor Verification

1. Run type check:

   npm run typecheck

2. Run tests:

   npm run test

3. Run linter:

   npm run lint

4. Build project:

   npm run build

Rules

• Never change behavior during refactor
• One refactor type at a time
• Commit after each successful refactor
• If tests fail, rollback immediately