Utility Types at a Glance

Partial & Pick

Partial<T> makes every property optional (great for update payloads). Pick<T, K> keeps only the listed keys.

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

type UserUpdate = Partial<User>;         // all fields optional
type UserPreview = Pick<User, "id" | "name">; // { id; name }

Omit & Record

Omit<T, K> keeps everything except the listed keys. Record<K, V> builds an object type mapping every key in K to type V.

type UserNoEmail = Omit<User, "email">;   // { id; name }
type Roles = "admin" | "editor" | "viewer";
type Permissions = Record<Roles, boolean>;
// { admin: boolean; editor: boolean; viewer: boolean }

Readonly<T>

Readonly<T> marks every property readonly, freezing the type without touching the original.

type FrozenUser = Readonly<User>;
const u: FrozenUser = { id: 1, name: "Ada", email: "a@x.com" };
u.name = "Bo";
// Error: Cannot assign to 'name' because it is a read-only property.

Compose them

Utility types nest: Readonly<Partial<Pick<User, "name" | "email">>> builds exactly the shape you need without a new interface.