Questions

Shalow Copy

Shalow Copy: Shalow copy upper se copy kr leta hn but deep copy nahi kr pata
example:

ye name ko or age ko copy kr ly ga but nested hoi hoi chezon ko nahi kr pay ga jese facebook twiiter ko copy nahi kr pay ga

use spread operator {...obj} to get deep copy from spread operator but it copy objects not deep and nested object

Deep Copy

Deep Copy:Deep copy deep tk objects ko copy kr leta hn means proper copy krna nested object and array ko deep copy krna.

ye niche ek method hn deep copy kar raha hn jo ke just practice ke liye hn, ye ham Interview me nahi batynge

ye niche ek recursive function hn jo ke deep copy kr raha hn object ki or arrays ki agr koi premitive data dynge to wo return kr dy ga

What is a Promise?

PromisesA Promise ek object hai jo asynchronous code ke result ko manage karta hai.
Yeh 3 states me ho sakta hai:

Pending: Initial state, na resolve hua hai na reject.
Fulfilled: Operation successfully complete ho gaya.
Rejected: Operation fail ho gaya.

How to Use Promises?

.then(): Jab promise resolve hota hai, .then() use karke uski resolved value ko access karte hain.
.catch(): Jab promise reject hota hai, .catch() us error ko handle karne ke liye use hota hai.
.finally(): Chahe promise resolve ho ya reject, .finally() hamesha execute hota hai.

Types of Promises

1) Promise.all()

Jab multiple promises parallel me execute ho rahe ho aur unka result ek saath chahiye ho, Promise.all() use karte hain.
Ek promise bhi fail kare to overall fail ho jata hai.

2) Promise.allSettled()

Yeh saare promises ke results return karta hai, chahe wo resolve ho ya reject.
Har promise ke result ke saath ek object deta hai { status: "fulfilled/rejected", value/reason: ... }.

Example:

Output:

3) Promise.race()

Jo promise sabse pehle resolve ya reject hota hai, uska result return karta hai.
Baaki promises ko ignore kar deta hai.

Example:

4) Promise.any() (ES2021)

Jo bhi pehla fulfilled promise hota hai, uska result return karta hai.
Agar saare promises reject ho jayein, tab AggregateError throw karta hai.

Example:

5) Promise.resolve()

Yeh ek resolved promise immediately return karta hai.

Example:

6) Promise.reject()

Yeh ek rejected promise immediately return karta hai.

Example:

Conclusion - Promises

Promise.all: Use jab saare promises resolve/reject hone ka result ek saath chahiye ho.
Promise.allSettled: Saare promises ke results chahiye, chahe resolved ho ya rejected.
Promise.race: Sabse pehle resolve/reject hone wale promise ka result chahiye.
Promise.any: Pehla successfully resolved promise chahiye.
Promise.resolve: Quick resolved promise banata hai.
Promise.reject: Quick rejected promise banata hai.

What is Methods

function inside object is called Methods

Spread Operator (...)

Spread operator ek modern JavaScript feature hai jo ek array ya object ke elements ko alag-alag (spread) karne ke liye use hota hai.

Example:

Rest Operator (...)

Rest operator ka use multiple elements ko ek array ya object ke andar "collect" karne ke liye hota hai. Ye zyada tar destructuring aur functions ke arguments handle karne ke liye use hota hai.

Example:

Use of Spread Operator and Rest Operator

Spread Operator:

Jab aapko elements ko expand karna ho.
For cloning or merging arrays/objects.
Function arguments pass karne ke liye.

Rest Operator:

Jab aapko multiple values ko ek array ya object mein collect karna ho.
Function parameters ke liye.
Array ya object destructuring ke liye.

Destructuring in JavaScript

Destructuring in JavaScriptDestructuring ek JavaScript syntax hai jo arrays aur objects ke elements ko extract (nikalne) aur unhe alag variables mein store karne ke liye use hoti hai. Iska kaam hai code ko concise aur readable banana.

Types of Destructuring:

Array Destructuring
Object Destructuring

1) Array Destructuring

Array destructuring ka use array ke elements ko alag variables mein extract karne ke liye hota hai.

2) Object Destructuring

Array destructuring ka use array ke elements ko alag variables mein extract karne ke liye hota hai.

Conclusion Destructuring ek powerful aur modern JavaScript feature hai jo code ko concise, readable, aur manageable banata hai. Ye har modern JavaScript developer ka tool hai, especially jab aapko APIs, React, ya complex data structures ke sath kaam karna ho.