Utility Types Trong TypeScript Bạn Nên Biết

interface User {
  name: string;
  email: string;
  age: number;
}
 
// Tất cả fields trở thành optional
type UpdateUser = Partial<User>;
 
// Tất cả fields trở thành required
type StrictUser = Required<User>;

// Chỉ lấy name và email
type UserPreview = Pick<User, 'name' | 'email'>;
 
// Bỏ age
type UserWithoutAge = Omit<User, 'age'>;

type Role = 'admin' | 'user' | 'guest';
 
const permissions: Record<Role, string[]> = {
  admin: ['read', 'write', 'delete'],
  user: ['read', 'write'],
  guest: ['read'],
};

type Status = 'active' | 'inactive' | 'pending' | 'deleted';
 
// Chỉ lấy active statuses
type ActiveStatus = Extract<Status, 'active' | 'pending'>;
// Result: 'active' | 'pending'
 
// Loại bỏ deleted
type VisibleStatus = Exclude<Status, 'deleted'>;
// Result: 'active' | 'inactive' | 'pending'

function createUser(name: string, age: number) {
  return { id: Math.random(), name, age };
}
 
type UserReturn = ReturnType<typeof createUser>;
// { id: number; name: string; age: number }
 
type UserParams = Parameters<typeof createUser>;
// [name: string, age: number]

type Response = Promise<{ data: User[] }>;
type Data = Awaited<Response>;
// { data: User[] }

// DeepPartial — recursive Partial
type DeepPartial<T> = {
  [P in keyof T]?: T[P] extends object ? DeepPartial<T[P]> : T[P];
};