TypeScript — Utility Types

Partial

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

function updateUser(user: Partial<User>) {
  // All properties optional
}

Required

interface Config {
  host?: string;
  port?: number;
}

function connect(config: Required<Config>) {
  // All properties required
}

Readonly

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

function process(user: Readonly<User>) {
  // user.name = 'Bob'; // Error
}

Pick

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

type UserBasic = Pick<User, 'name' | 'age'>;

Omit

type UserWithoutEmail = Omit<User, 'email'>;

Record

type UserRoles = Record<string, string[]>;
const roles: UserRoles = {
  admin: ['read', 'write'],
  user: ['read']
};

Mini Practice

1. Use Partial
2. Use Required
3. Use Pick and Omit
4. Create Record types

Up Next

Continue with Mapped Types - Type transformation.