Chapter 8TypeScript~1 min read

Enums आणि Utility Types

TypeScript चे Powerful Built-ins

TypeScript मध्ये काही built-in utility types आहेत जे existing types manipulate करतात — Partial, Required, Pick, Omit, Record. हे production code मध्ये खूप useful आहेत.

Enum — named constants

typescript

// Numeric enum
enum Direction {
  Up,    // 0
  Down,  // 1
  Left,  // 2
  Right, // 3
}

// String enum (better for debugging)
enum UserRole {
  Admin = "ADMIN",
  User = "USER",
  Guest = "GUEST",
}

function handleRole(role: UserRole): void {
  if (role === UserRole.Admin) {
    console.log("Full access!");
  }
}

handleRole(UserRole.Admin);
handleRole("ADMIN"); // ❌ ERROR

Utility Types

typescript

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

// Partial<T> — सगळ्या properties optional करतो
type PartialUser = Partial<User>;
// { id?: number; name?: string; email?: string; password?: string }

// Required<T> — सगळ्या properties required करतो
type RequiredUser = Required<PartialUser>;

// Pick<T, Keys> — फक्त select properties घ्या
type PublicUser = Pick<User, "id" | "name" | "email">;

// Omit<T, Keys> — select properties वगळा
type UserWithoutPassword = Omit<User, "password">;

// Record<Keys, Type> — object type बनवा
type RolePermissions = Record<UserRole, string[]>;

💡

API response बनवताना Omit<User, "password"> — हे pattern खूप common आहे. Password कधीही frontend ला पाठवू नका!

✅ Key Points — लक्षात ठेवा

▸Enum — named constants group
▸String enums — debugging मध्ये helpful
▸Partial<T> — सगळं optional
▸Pick<T, K> — select properties
▸Omit<T, K> — properties हटवा

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