Optional & Readonly Properties
? symbol, EK, property, ko, OPTIONAL, banaता hai — WOH, PRESENT, ho, sakti, hai, YA, NAHI, bhi, ho, sakti. Optional, properties, ko, ACCESS, karne, se, PEHLE, CHECK, karna, aksar, ZAROORI, hoti, hai.
readonly, keyword, EK, PROPERTY, ko, INITIALIZATION, ke, BAAD, MODIFY, hone, se, ROKТA, hai — jaise, EK, id, field, JO, EK, BAAR, SET, hone, ke, BAAD, KABHI, CHANGE, NAHI, honi, CHAHIYE.
interface Product {
readonly id: number;
name: string;
discount?: number; // optional
}
const product: Product = { id: 1, name: "Laptop" };
// product.id = 2; // ERROR — readonly property, modify, nahi, ho, sakti
console.log(product.discount ?? 0); // undefined, agar, discount, na, di, gayi, ho- ? = property, optional, hai, present, ho, sakti, hai, ya, NAHI
- readonly = property, initialization, ke, BAAD, modify, nahi, ki, ja, sakti
- Optional chaining (?.) aur, nullish, coalescing, (??) optional, properties, ke, saath, USEFUL, hain
readonly, property, khud, ko, REASSIGN, hone, se, ROKТА, hai, LEKIN, agar, VALUE, EK, array/object, hai, USke, ANDAR, ke, CONTENTS, ko, MODIFY, kiya, ja, sakta hai — jab, tak, ki, ARRAY, KHUD, bhi, readonly, na, ho.
interface Config {
readonly tags: string[];
}
const c: Config = { tags: ["a"] };
c.tags.push("b"); // OK — array, khud, readonly, nahi, hai
// c.tags = []; // ERROR — property, hi, reassign, nahi, ho, saktiEk, OPTIONAL, property, (age?: number), age: number | undefined, ke, similar, hai, LEKIN, EK, IMPORTANT, DIFFERENCE, ke, saath — optional, properties, ko, OBJECT, mein, COMPLETELY, OMIT, kiya, ja, sakta hai, undefined, VALUE, ke, saath, EXPLICITLY, SET, karne, ki, ZAROORAT, nahi.