Practice Questions — Arrays and Array Methods

const arr = [10, 20, 30];
console.log(arr[1]);

const arr = [1, 2, 3];
arr.push(4);
console.log(arr);

const arr = ["a", "b", "c"];
console.log(arr.length);
console.log(arr[arr.length - 1]);

const nums = [5, 10, 15];
const doubled = nums.map(n => n * 2);
console.log(doubled);

const nums = [1, 2, 3, 4, 5];
const even = nums.filter(n => n % 2 === 0);
console.log(even);

const arr = [10, 20, 30];
console.log(arr.includes(20));
console.log(arr.includes(25));

const nums = [1, 2, 3, 4, 5];
const sum = nums.reduce((acc, n) => acc + n, 0);
console.log(sum);

const arr = [3, 1, 4, 1, 5];
const sorted = [...arr].sort((a, b) => a - b);
console.log(sorted);
console.log(arr);

const arr = [1, 2, 3, 4, 5];
console.log(arr.slice(1, 4));
console.log(arr.slice(3));

const students = [
  { name: "Aarav", score: 72 },
  { name: "Priya", score: 91 },
  { name: "Rohan", score: 85 }
];

const top = students.find(s => s.score > 80);
console.log(top.name);

const [a, b, ...rest] = [10, 20, 30, 40, 50];
console.log(a);
console.log(b);
console.log(rest);

const nums = [1, 2, 3, 4, 5, 6];
const result = nums
  .filter(n => n % 2 === 0)
  .map(n => n * n);
console.log(result);

const words = ["hello", "world", "javascript"];
const result = words.reduce((longest, word) => {
  return word.length > longest.length ? word : longest;
}, "");
console.log(result);

const nums = [1, 2, 3, 4, 5];
const result = nums.reduce((acc, n) => {
  acc[n % 2 === 0 ? "even" : "odd"].push(n);
  return acc;
}, { even: [], odd: [] });
console.log(result);

const a = [1, 2, 3];
const b = [3, 4, 5];
const unique = [...new Set([...a, ...b])];
console.log(unique);

const ages = [12, 18, 15, 21, 16];
console.log(ages.every(a => a >= 18));
console.log(ages.some(a => a >= 18));

const arr = ["a", "b", "c"];
const removed = arr.pop();
console.log(removed);
console.log(arr);

const data = [[1, 2], [3, 4], [5, 6]];
const flat = data.flat();
const sum = flat.reduce((a, b) => a + b, 0);
console.log(flat);
console.log(sum);

const arr = [1, 2, 3, 4, 5];
const idx = arr.findIndex(n => n > 3);
console.log(idx);

const arr = ["x", "y", "z"];
arr.unshift("w");
console.log(arr);

const names = ["Aarav", "Priya", "Rohan"];
console.log(names.indexOf("Priya"));
console.log(names.indexOf("Diya"));

const nums = [10, 20, 30, 40, 50];
const result = nums
  .filter(n => n >= 20)
  .map(n => n / 10);
console.log(result);

const a = [1, 2];
const b = [3, 4];
const c = [...a, ...b, 5];
console.log(c);

const arr = ["hello", "world", "test"];
const result = arr.map(s => s.toUpperCase());
console.log(result);

const scores = [85, 42, 91, 67, 38];
const passCount = scores.filter(s => s >= 50).length;
console.log(passCount);

const students = [
  { name: "Aarav", marks: 85 },
  { name: "Priya", marks: 92 },
  { name: "Rohan", marks: 78 },
  { name: "Diya", marks: 95 }
];

const toppers = students
  .filter(s => s.marks >= 85)
  .sort((a, b) => b.marks - a.marks)
  .map(s => s.name);

console.log(toppers);

const words = ["cat", "elephant", "dog", "hippopotamus"];
const longest = words.reduce((a, b) => a.length >= b.length ? a : b);
console.log(longest);

const arr = Array.from({ length: 5 }, (_, i) => i * i);
console.log(arr);

const data = [
  { category: "fruit", name: "apple" },
  { category: "veg", name: "carrot" },
  { category: "fruit", name: "mango" },
  { category: "veg", name: "potato" }
];

const grouped = data.reduce((acc, item) => {
  if (!acc[item.category]) acc[item.category] = [];
  acc[item.category].push(item.name);
  return acc;
}, {});

console.log(grouped);

const arr = [1, 2, 3, 4];
const shifted = arr.shift();
console.log(shifted);
console.log(arr);

const sentences = ["hello world", "foo bar baz"];
const words = sentences.flatMap(s => s.split(" "));
console.log(words);