15_important_question.js

/**
 * JavaScript Array Methods — 10 Important Examples
 * Topic: Most commonly used array methods (interview favorites)
 */

// 1. map() — har element ko transform karo
const nums1 = [1, 2, 3, 4];
const doubled = nums1.map(n => n * 2);
console.log("1. map():", doubled); // [2, 4, 6, 8]


// 2. filter() — condition ke basis pe elements chuno
const nums2 = [1, 2, 3, 4, 5, 6];
const evens = nums2.filter(n => n % 2 === 0);
console.log("2. filter():", evens); // [2, 4, 6]


// 3. reduce() — sab kuch ek value mein combine karo
const prices = [100, 200, 300];
const total = prices.reduce((sum, price) => sum + price, 0);
console.log("3. reduce():", total); // 600


// 4. forEach() — bas loop chalao, kuch return nahi karna
const fruits = ["apple", "mango", "banana"];
fruits.forEach(fruit => console.log("4. forEach():", fruit));


// 5. find() — pehla matching element dhoondo
const users = [{ id: 1, name: "Aman" }, { id: 2, name: "Riya" }];
const user = users.find(u => u.id === 2);
console.log("5. find():", user); // {id: 2, name: "Riya"}


// 6. some() — check karo koi ek condition satisfy karta hai kya
const nums3 = [1, 3, 5, 8];
const hasEven = nums3.some(n => n % 2 === 0);
console.log("6. some():", hasEven); // true


// 7. every() — check karo SAB elements condition satisfy karte hain
const ages = [22, 25, 19, 30];
const allAdults = ages.every(age => age >= 18);
console.log("7. every():", allAdults); // true


// 8. sort() — array ko order mein lagao
const nums4 = [5, 2, 9, 1];
nums4.sort((a, b) => a - b); // ascending
console.log("8. sort():", nums4); // [1, 2, 5, 9]


// 9. includes() — element hai ya nahi, quick check
const skills = ["React", "Node", "MongoDB"];
console.log("9. includes():", skills.includes("Node")); // true


// 10. Chaining — sab methods ko combine karke real-world use
const products = [
  { name: "Laptop", price: 50000, inStock: true },
  { name: "Phone", price: 20000, inStock: false },
  { name: "Tablet", price: 15000, inStock: true },
];

const totalAvailableValue = products
  .filter(p => p.inStock)
  .map(p => p.price)
  .reduce((sum, price) => sum + price, 0);

console.log("10. Chaining:", totalAvailableValue); // 65000