TypeScript Language Expertise

Overview

Type-safe, production-quality TypeScript: the type system's sharp edges, strict-mode config that actually moves the needle, the type-vs-runtime boundary, and framework patterns (zod/tRPC/Prisma/React/Express). Assumes fluency with JS and basic TS — this is reference for the traps and idioms that bite experienced engineers.

Type System Essentials

Generics

// Constraints + default type param; `this` return for fluent chaining
interface HasId { id: string }
class Repo<T extends HasId = HasId> {
  private items = new Map<string, T>();
  save(item: T): this { this.items.set(item.id, item); return this; }
  find(id: string): T | undefined { return this.items.get(id); }
}