TypeScript Patterns — Advanced

This skill extends typescript-patterns with the type system internals, advanced generics, async patterns, testing, and runtime performance.

When to Activate

• Building type-safe library APIs with advanced generics
• Writing type-level transformations (mapped/conditional types)
• Testing TypeScript with Vitest or Jest
• Optimizing TypeScript compilation and bundle size
• Extracting route parameter names from URL patterns using template literal types and infer
• Debugging slow TypeScript compilation caused by deep recursive conditional types
• Creating decorator-based patterns for logging, validation, or method interception in TypeScript 5+

Mapped Types

Transform one object type into another by iterating over keys: