TypeScript Generics: The Patterns I Actually Use, Not the Ones in Tutorials

Generics tutorials love a `Stack<T>` example that's technically correct and never resembles anything in a real codebase. In practice, the generics that pull their weight in application code show up in a much narrower, more useful set of places.

• API response wrappers — `ApiResponse<T>` typed once, reused across every endpoint, catching shape mismatches at compile time.
• Reusable data-fetching hooks (`useQuery<TData>`) so a single hook serves every resource type with full inference.
• Constrained generics (`<T extends { id: string }>`) when a function needs to guarantee a shape without knowing the full type.
• Utility types built from `keyof` and mapped types for form state, so field names stay in sync with a model automatically.

The generics that earn their complexity are the ones solving a real duplication problem — the same logic written once instead of five times with five slightly different types. If a generic isn't removing duplication, it's usually adding ceremony instead of value.

A generic that doesn't remove real duplication is decoration. The useful ones are boring, and they show up in every API layer.