Utility Types

TypeScript provides built-in utility types for common type transformations.

Partial & Required

interface User {
  name: string;
  age: number;
  email: string;
}

type PartialUser = Partial<User>;  // All optional
type RequiredUser = Required<User>;  // All required

const update: PartialUser = { age: 31 };

Pick & Omit

interface User {
  id: number;
  name: string;
  email: string;
  password: string;
}

type PublicUser = Omit<User, "password">;
type UserCredentials = Pick<User, "email" | "password">;

Record

type Role = "admin" | "user" | "guest";

const permissions: Record<Role, string[]> = {
  admin: ["read", "write", "delete"],
  user: ["read", "write"],
  guest: ["read"]
};

ReturnType & Parameters

function getUser() {
  return { id: 1, name: "Alice" };
}

type User = ReturnType<typeof getUser>;

function greet(name: string, age: number) {
  console.log(`${name} is ${age}`);
}

type GreetParams = Parameters<typeof greet>;  // [string, number]