Classes aur Objects

Ek class data (properties) ko un functions (methods) ke saath bundle karti hai jo usper kaam karte hain — bilkul JavaScript jaisa hi idea, lekin TypeScript access modifiers add karta hai jo control karte hain ki ek property ya method kahan se use ki ja sakti hai.

class Dog {
  name: string;
  private age: number;

  constructor(name: string, age: number) {
    this.name = name;
    this.age = age;
  }

  bark(): string {
    return `${this.name} says Woof! (age ${this.age})`;
  }
}

const rex = new Dog("Rex", 3);
console.log(rex.name);
console.log(rex.bark());

Rex
Rex says Woof! (age 3)

public, private, protected, aur readonly

• public default hota hai — kahin se bhi accessible hai, class ke bahar se bhi
• private sirf class ke andar se hi accessible hota hai — rex.age, Dog ke bahar ek compile error hoga
• protected private jaisa hi hai, lekin subclasses se bhi accessible hota hai
• readonly ko in mein se kisi ke bhi saath combine kiya ja sakta hai, aur ise sirf ek baar set kiya ja sakta hai, usually constructor mein

Constructor shorthand

Har property ke liye this.name = name likhna repetitive ho jaata hai — TypeScript aapko iske bajaye ek property ko directly constructor ki parameter list mein declare aur assign karne deta hai.

class Point {
  constructor(public x: number, public y: number) {}

  toString(): string {
    return `(${this.x}, ${this.y})`;
  }
}

const p = new Point(3, 4);
console.log(p.toString());

(3, 4)

Aage: generics — ek aisa function ya type likhna jo kai types ke across kaam kare, type safety khoye bina.