DRY Refactoring

Process

1. Identify - Exact copies, similar patterns, parallel hierarchies, naming patterns (data1/data2, handleXClick)
2. Analyze - Coupling, cohesion, frequency (Rule of Three: wait for 3+ occurrences), volatility
3. Refactor - Choose technique below, extract incrementally, test after each step

Techniques

Extract Function - Same logic in multiple places

getFullName(user: User) => `${user.firstName} ${user.lastName}`

Extract Variable - Repeated expression