Why Patterns Matter
TypeScript’s type system is powerful, but raw power doesn’t help unless you reach for the right shape at the right moment. Over the years a handful of patterns have become muscle memory.
1. Discriminated Unions
Tagged unions turn runtime branching into a compile-time guarantee. The compiler narrows for you when you check the tag.
type Result<T> =
| { ok: true; value: T }
| { ok: false; error: string };2. as const for Literal Inference
Lock literal types without verbose annotations. Great for action constants and route maps.
3. Branded Types
Prevent mixing up UserId and OrderId even though both are strings underneath. A simple intersection with a phantom brand does the job.
4. satisfies Over Type Assertion
satisfies checks the shape without widening — you keep the inferred literal types while still getting type safety.
5. Utility Type Composition
Pick, Omit, Partial, and ReturnType compose like LEGO. Most “complex” types are just three utility types in a trench coat.
These five patterns cover 80% of the type gymnastics I do day to day.