typescript-advanced

---
name: typescript-advanced
description: Advanced TypeScript patterns including generics, conditional types, mapped types, template literals, and type guards
---

# TypeScript Advanced

## Generics with Constraints

```typescript
interface HasId {
  id: string;
}

function findById<T extends HasId>(items: T[], id: string): T | undefined {
  return items.find(item => item.id === id);
}

function groupBy<T, K extends string | number>(
  items: T[],
  keyFn: (item: T) => K
): Record<K, T[]> {
  r