The Language

The Language - Volume I of the In Types We Trust series - is a deep, modern guide to the TypeScript type system itself: not the tooling, not the framework glue, but the language of types you write every day and the compiler that reasons about them.

It's written for JavaScript and TypeScript developers who want to go from "I add types until the red squiggles disappear" to genuinely modeling their domain - so that entire classes of bugs simply cannot compile.

Inside, you'll master:

- Unions, literal types, and narrowing - how TypeScript reasons about control flow
- Type inference: what the compiler already knows, and how to work with it instead of against it
- Generics, constraints, and conditional types - reusable, precise, self-checking APIs
- Type-level programming: mapped types, template literals, and the patterns behind libraries like Zod and tRPC
- Modeling techniques that make illegal states unrepresentable

Every concept is grounded in practical, idiomatic TypeScript and illustrated with diagrams and worked examples, current to the 2026 TypeScript ecosystem.

If you can already write TypeScript and now want to truly understand it - and let the compiler carry the weight - start here.

Volume I of three. Reads perfectly on its own.