Generics

What are Generics?

Generics let you write reusable code that works with multiple types while retaining type safety. Think of them as type variables.

function identity<T>(arg: T): T { return arg }

The T is a type parameter. When you call identity("hello"), TypeScript infers T as string.

Generic Constraints

You can constrain what types a generic can accept using extends.

function getLength<T extends { length: number }>(arg: T): number { return arg.length }

Generic Interfaces and Classes

Interfaces and classes can also be generic, making them incredibly flexible building blocks.