معرفی کامل Generic Utility Types در TypeScript + مثال‌های کاربردی

// UtilityType<TypeYouPass>

Readonly<{ name: string; age: number }>

// Readonly<T>

type User = {
  name: string;
  age: number;
};

type ReadonlyUser = Readonly<User>;

const user: ReadonlyUser = {
  name: "Ali",
  age: 30,
};

user.age = 31; // ❌ Error: Cannot assign to 'age' because it is a read-only property

// Partial<T>

type User = {
  name: string;
  age: number;
};

type UpdateUser = Partial<User>;

const update: UpdateUser = {
  name: "Reza", // ✅ OK
  // age is optional now
};

// Required<T>

type User = {
  name?: string;
  age?: number;
};

type CompleteUser = Required<User>;

const u: CompleteUser = {
  name: "Ali", // ✅ Both required now
  age: 25,
};

// Pick<T, Keys>

type User = {
  id: number;
  name: string;
  email: string;
};

type PublicProfile = Pick<User, "id" | "name">;

// Result:
// { id: number; name: string; }

// Omit<T, Keys>

type User = {
  id: number;
  name: string;
  email: string;
};

type WithoutEmail = Omit<User, "email">;

// Result:
// { id: number; name: string; }

type Nullable<T> = {
  [K in keyof T]: T[K] | null;
};

type User = { name: string; age: number };

type NullableUser = Nullable<User>;
// Result: { name: string | null; age: number | null }