Interface (ইন্টারফেস)

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

function greet(user: User): string {
  return "হ্যালো, " + user.name;
}

const u: User = { name: "রহিম", age: 28 };
console.log(greet(u));

interface Profile {
  name: string;
  email?: string;           // optional
  readonly joinedAt: Date;  // readonly
}

const p: Profile = {
  name: "রহিম",
  joinedAt: new Date(),
};

// p.joinedAt = new Date();  // ❌ readonly

interface Comparator {
  (a: number, b: number): number;
}

const sortBy: Comparator = (a, b) => a - b;
console.log(sortBy(3, 9));   // -6

interface Address {
  city: string;
  zip: string;
}

interface Customer {
  name: string;
  address: Address;    // nested
}

const c: Customer = {
  name: "করিম",
  address: { city: "ঢাকা", zip: "1207" },
};

interface Animal {
  name: string;
}

interface Dog extends Animal {
  breed: string;
}

const myDog: Dog = {
  name: "টমি",
  breed: "স্প্যানিয়েল",
};

interface Printable {
  print(): void;
}

interface Serializable {
  toJSON(): string;
}

interface Report extends Printable, Serializable {
  build(): string;
}

// Report-এ তিনটির সব দাবি একসাথে থাকে

interface Window {
  version: number;
}

interface Window {
  appName: string;
}

// দুই ঘোষণা মিশে যায় → { version: number; appName: string }