অ্যারের হাইয়ার-অর্ডার মেথড (Array Higher-Order Methods)

let prices = [10, 25, 50, 75, 100];

// .map() — transform each item
let withTax = prices.map(price => price * 1.1);
console.log(withTax); // [11, 27.5, 55, 82.5, 110]

// .filter() — keep items that pass a test
let affordable = prices.filter(price => price <= 50);
console.log(affordable); // [10, 25, 50]

// .reduce() — combine into one value
let total = prices.reduce((sum, price) => sum + price, 0);
console.log(total); // 260

// 🔥 Chain them together!
let affordableTotal = prices
  .filter(price => price <= 50)     // [10, 25, 50]
  .map(price => price * 1.1)        // [11, 27.5, 55]
  .reduce((sum, p) => sum + p, 0);  // 93.5
console.log(affordableTotal); // 93.5

[11, 27.5, 55, 82.5, 110]
[10, 25, 50]
260
93.5

let users = [
  { name: "Anika", age: 28 },
  { name: "Rafi", age: 17 },
  { name: "Sadia", age: 35 },
  { name: "Tariq", age: 15 }
];

// .find() — first match
let firstAdult = users.find(u => u.age >= 18);
console.log(firstAdult); // { name: "Anika", age: 28 }

// .findIndex() — index of first match
let idx = users.findIndex(u => u.name === "Sadia");
console.log(idx); // 2

// .some() — is at least one person under 18?
console.log(users.some(u => u.age < 18)); // true

// .every() — is everyone over 18?
console.log(users.every(u => u.age >= 18)); // false

// .includes() — simple value check (no callback)
let nums = [1, 2, 3, 4, 5];
console.log(nums.includes(3)); // true
console.log(nums.includes(9)); // false

{ name: "Anika", age: 28 }
2
true
false
true
false

// .sort() — default is alphabetical (even for numbers!)
let nums = [30, 1, 100, 5, 20];
nums.sort();
console.log(nums); // [1, 100, 20, 30, 5] — WRONG for numbers!

// Sort numbers correctly with a compare function
nums.sort((a, b) => a - b); // ascending
console.log(nums); // [1, 5, 20, 30, 100]

nums.sort((a, b) => b - a); // descending
console.log(nums); // [100, 30, 20, 5, 1]

// Sort objects by a property
let students = [
  { name: "Zara", grade: 92 },
  { name: "Asif", grade: 88 },
  { name: "Mita", grade: 95 }
];
students.sort((a, b) => b.grade - a.grade);
console.log(students.map(s => `${s.name}: ${s.grade}`));

// .forEach() — do something for each item (no return value)
["আম", "জাম", "কাঁঠাল"].forEach((fruit, i) => {
  console.log(`${i + 1}. ${fruit}`);
});

[1, 100, 20, 30, 5]
[1, 5, 20, 30, 100]
[100, 30, 20, 5, 1]
["Mita: 95", "Zara: 92", "Asif: 88"]
1. আম
2. জাম
3. কাঁঠাল