Generics – Basics

Generic Functions

function identity<T>(value: T): T {
  return value;
}

const num = identity(42);   // T inferred as number
const str = identity("hi"); // T inferred as string

Generic Interfaces

interface Pair<T, U> {
  first: T;
  second: U;
}

const p: Pair<number, string> = { first: 1, second: "one" };

Default Generic Types

function wrap<T = string>(value: T) {
  return { value };
}

wrap(123); // T inferred as number
wrap();    // T defaults to string → { value: "" }