5 TypeScript Utility Types You Should Know

TypeScript is powerful, but are you using its full potential? Utility types are built-in tools to transform types efficiently.

1. Partial

Makes all properties of a type optional. Great for update functions.

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

function updateUser(id: number, fields: Partial<User>) {
  // fields.name is optional now
}

2. Pick<T, K>

Selects only specific keys from a type.

type UserSummary = Pick<User, 'id' | 'name'>;
// { id: number; name: string; }

3. Omit<T, K>

The opposite of Pick. Removes specific keys.

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

4. Record<K, T>

Creates an object type with specific keys and values.

const roles: Record<string, number> = {
  'admin': 1,
  'user': 2
};

5. Readonly

Prevents mutation of properties.

const config: Readonly<Config> = { endpoint: 'api.com' };
// config.endpoint = 'error'; // Error!