Partial, Readonly, Record, Pick, Omit

Pendahuluan

Partial

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

type UserUpdate = Partial<User>;
const patch: UserUpdate = { name: "Ada" }; // only changed fields

Readonly

type Config = Readonly<{ api: string; timeout: number }>;
const cfg: Config = { api: "https://api", timeout: 1000 };
// cfg.timeout = 2000; // Error: readonly

Record

type Status = "idle" | "loading" | "error";
type Flags = Record<Status, boolean>;
const f: Flags = { idle: true, loading: false, error: false };

// Also works for arbitrary string keys
const scores: Record<string, number> = { math: 95, eng: 88 };

Pick dan Omit

interface User {
  id: number;
  name: string;
  email?: string;
  role: "user" | "admin";
}

type PublicUser = Pick<User, "id" | "name">;
type PrivateUser = Omit<User, "role">;

const pu: PublicUser = { id: 1, name: "Ada" };
const pr: PrivateUser = { id: 1, name: "Ada", email: "a@x.io" };

Tips

Pemeriksaan utilitas Record

Rangkuman