Generic Functions & Interfaces

Generic Functions & Interfaces

Generics allow creating reusable components that work over a variety of types while retaining type safety.

Generic Functions

Instead of using any, use a type parameter like <T>:

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

let num = identity<number>(42);     // Explicit type argument
let str = identity("Hello World"); // Type inferred as string!

Generic Interfaces

Interfaces can also accept type parameters:

interface ApiResponse<Data> {
  status: number;
  message: string;
  data: Data;
}

type UserResponse = ApiResponse<{ id: string; name: string }>;
type ProductsResponse = ApiResponse<string[]>;

Multiple Type Parameters

function pairValues<K, V>(key: K, value: V): [K, V] {
  return [key, value];
}

TL;DR

• Generics use angle brackets <T> to parameterize types.
• They preserve exact type relationships between inputs and outputs.
• TypeScript can infer generic types automatically from argument values.