Utility Types

TypeScript ships several built-in generic types that transform an existing type into a new one, without redeclaring it from scratch.

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

type PartialUser = Partial<User>;         // all properties optional
type UserPreview = Pick<User, "name">;     // only "name"
type UserNoEmail = Omit<User, "email">;    // everything except "email"
type ReadonlyUser = Readonly<User>;        // no property can be reassigned

These are especially common when writing a function that only needs to update some fields of an object (Partial<User>), or expose a limited public view of a larger internal type (Pick/Omit).