JavaScript Array Methods & Properties Kya Hote Hain?

Data collections ko efficiently manage aur manipulate karna sikhein.

Array Properties

Array properties arrays ke basic attributes ko define karti hain.

1. `length` Property

Yeh property array me total kitne elements hain, yeh batata hai. Yeh loops aur data manipulation ke liye bahut useful hoti hai.

let fruits = ["Apple", "Mango", "Banana"];
console.log(fruits.length); // Output: 3

Array Methods

JavaScript me array ke saath kaam karne ke liye bahut saare methods hote hain.

1. Adding & Removing Elements

Method	Description
`push()`	Array ke end me ek ya zyada elements add karta hai.
`pop()`	Array ka last element remove karta hai.
`unshift()`	Array ke beginning me ek ya zyada elements add karta hai.
`shift()`	Array ka first element remove karta hai.

let numbers = [10, 20];
numbers.push(30);     // [10, 20, 30]
numbers.pop();        // [10, 20]
numbers.unshift(5);   // [5, 10, 20]
numbers.shift();      // [10, 20]

2. Extracting & Manipulating Arrays

Method	Description
`slice(start, end)`	Array ka ek portion return karta hai bina original array ko badle.
`splice(start, count, items...)`	Elements ko add, remove, ya replace karta hai aur original array ko modify karta hai.

let fruits = ["Apple", "Banana", "Mango", "Orange"];
let sliced = fruits.slice(1, 3); // ["Banana", "Mango"]

fruits.splice(1, 2, "Grapes", "Kiwi"); 
// fruits is now ["Apple", "Grapes", "Kiwi", "Orange"]

3. Iterating (Looping) Methods

forEach(): Array ke har element ke liye ek function run karta hai.
map(): Ek naya array return karta hai jisme har element par function apply karne ka result hota hai.
filter(): Ek naya array return karta hai jisme sirf woh elements hote hain jo condition ko pass karte hain.
reduce(): Array ke sabhi elements ko ek single value me reduce karta hai.

const numbers = [1, 2, 3, 4, 5];

// map: Double each number
const doubled = numbers.map(num => num * 2); // [2, 4, 6, 8, 10]

// filter: Get only even numbers
const evens = numbers.filter(num => num % 2 === 0); // [2, 4]

// reduce: Calculate the sum
const sum = numbers.reduce((total, num) => total + num, 0); // 15

4. Searching Methods

Method	Description
`indexOf()`	Element ka pehla index return karta hai, ya -1 agar nahi milta.
`lastIndexOf()`	Element ka aakhri index return karta hai.
`includes()`	Agar element exist karta hai toh `true` return karta hai, nahi toh `false`.
`find()`	Condition pass karne wala pehla element return karta hai.
`findIndex()`	Condition pass karne wale pehle element ka index return karta hai.

const fruits = ["Apple", "Banana", "Mango", "Banana"];
console.log(fruits.indexOf("Banana"));     // 1
console.log(fruits.lastIndexOf("Banana")); // 3
console.log(fruits.includes("Mango"));      // true

Key Takeaways

length property array ka size batata hai.
push() aur pop() end se elements add/remove karte hain.
unshift() aur shift() start se elements add/remove karte hain.
map(), filter(), aur reduce() powerful methods hain jo original array ko change kiye bina naye arrays ya values create karte hain.
slice() se array ka part copy hota hai, jabki splice() original array ko modify karta hai.

Bonus: Practical Application!

Ab in methods ko practically use karke dekhein.

Ek numbers ka array banayein aur `map` ka use karke ek naya array create karein jisme har number ka double ho. Fir, `filter` ka use karke sirf 10 se bade numbers ko select karein.

Practice in JS Editor

Test Your Knowledge!

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