JavaScript Arrays: Intermediate (অ্যারে)

const prices = [100, 250, 300];

const withVat = prices.map(p => p * 1.15);

console.log(withVat); // [115, 287.5, 345]
console.log(prices);  // [100, 250, 300] — মূল অপরিবর্তিত

const prices = [100, 250, 300, 150];

const onSale = prices.filter(p => p < 250);

console.log(onSale); // [100, 150]

const prices = [100, 250, 300, 150];

const found = prices.find(p => p === 300);
console.log(found); // 300 (প্রথম মিলে যাওয়া মান)

const i = prices.findIndex(p => p === 300);
console.log(i); // 2 (সূচক)

console.log(prices.find(p => p === 999)); // undefined

const scores = [70, 85, 90];

const anyFail = scores.some(s => s < 40);   // কোনো একটা ৪০-এর নিচে?
const allPass = scores.every(s => s >= 40); // সবগুলো কি পাশ?

console.log(anyFail);  // false
console.log(allPass);  // true

const fruits = ["আম", "কলা", "কমলা"];

console.log(fruits.includes("কলা")); // true
console.log(fruits.includes("লিচু")); // false

console.log(fruits.indexOf("কলা"));  // 1
console.log(fruits.indexOf("লিচু"));  // -1 (খুঁজে পাওয়া যায়নি)

const numbers = [10, 20, 30];

const total = numbers.reduce((sum, n) => sum + n, 0);

console.log(total); // 60

const fruits = ["আম", "কলা", "কমলা", "লিচু"];

const sliced = fruits.slice(1, 3); // নতুন array: ["কলা", "কমলা"]
console.log(sliced);
console.log(fruits); // মূল অপরিবর্তিত

const removed = fruits.splice(1, 2, "আঙুর"); // ১ থেকে ২টি বাদ, জায়গায় "আঙুর"
console.log(removed); // ["কলা", "কমলা"]
console.log(fruits);  // ["আম", "আঙুর", "লিচু"]

const a = [1, 2];
const b = [3, 4];

const c = a.concat(b);
const d = [...a, ...b];

console.log(c); // [1, 2, 3, 4]
console.log(d); // [1, 2, 3, 4]

const copy = [...a]; // অনুলিপি
copy.push(99);
console.log(a);    // [1, 2] — মূল অপরিবর্তিত
console.log(copy); // [1, 2, 99]

const [first, second, ...rest] = [10, 20, 30, 40];

console.log(first);  // 10
console.log(second); // 20
console.log(rest);   // [30, 40]

const [, , third] = [10, 20, 30, 40];
console.log(third);  // 30 (ফাঁকা জায়গা দিয়ে স্কিপ)

const nums = [3, 1, 10, 2];

const sorted = [...nums].sort((x, y) => x - y);
console.log(sorted); // [1, 2, 3, 10]

// spread না করে সরাসরি sort করলে মূল array-ও বদলায়!
const reversed = [...nums].reverse();
console.log(reversed); // [2, 10, 1, 3]

const matrix = [
  [1, 2, 3],
  [4, 5, 6],
  [7, 8, 9],
];

console.log(matrix[0][1]); // 2
console.log(matrix[2][0]); // 7

const flat = matrix.flat();
console.log(flat); // [1, 2, 3, 4, 5, 6, 7, 8, 9]

const products = [
  { id: 1, name: "মোবাইল", price: 15000 },
  { id: 2, name: "ল্যাপটপ", price: 65000 },
  { id: 3, name: "হেডফোন", price: 2000 },
];

const names = products.map(p => p.name);
console.log(names); // ["মোবাইল", "ল্যাপটপ", "হেডফোন"]

const cheap = products.filter(p => p.price < 10000);
console.log(cheap.map(p => p.name)); // ["হেডফোন"]

const total = products.reduce((sum, p) => sum + p.price, 0);
console.log(total); // 82000