TypeScript Refactoring Patterns

Core Principles

1. Type Narrowing Over Type Assertions - Use type guards and discriminated unions instead of as casts
2. Const Assertions for Literals - Use as const for immutable literal types
3. Generic Constraints - Prefer extends constraints over any
4. Branded Types - Use branded types for domain-specific validation

Refactoring Patterns

Extract Discriminated Union

When you see multiple boolean flags, refactor to discriminated union: