JavaScript Array Methods and Programs

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An array is a collection of elements stored in a single variable.

let fruits = ["apple", "banana", "mango"];

🔹 Categories of Array Methods

To make things easier, we’ll group methods into:

  1. Basic / Access Methods
  2. Add / Remove Elements
  3. Iteration Methods
  4. Transformation Methods
  5. Search / Find Methods
  6. Utility Methods

🔹 1. Basic / Access Methods

✅ length

Returns number of elements

let arr = [1, 2, 3];
console.log(arr.length); // 3

✅ toString()

Converts array to string

let arr = [1, 2, 3];
console.log(arr.toString()); // "1,2,3"

✅ at()

Access element using index (supports negative index)

let arr = [10, 20, 30];
console.log(arr.at(-1)); // 30

🔹 2. Add / Remove Elements

✅ push()

Adds element at end

let arr = [1, 2];
arr.push(3); // [1,2,3]

✅ pop()

Removes last element

arr.pop(); // removes 3

✅ unshift()

Adds element at beginning

arr.unshift(0); // [0,1,2]

✅ shift()

Removes first element

arr.shift(); // removes 0

✅ splice()

Add/remove elements at specific index

let arr = [1, 2, 3, 4];
arr.splice(1, 2); // removes 2,3 → [1,4]

🔹 3. Iteration Methods

✅ forEach()

Executes function for each element

arr.forEach((item) => console.log(item));

✅ map()

Returns new array after transformation

let nums = [1, 2, 3];
let doubled = nums.map(n => n * 2);
// [2,4,6]

✅ filter()

Returns elements that match condition

let nums = [1, 2, 3, 4];
let even = nums.filter(n => n % 2 === 0);
// [2,4]

✅ reduce()

Reduces array to single value

let nums = [1, 2, 3];
let sum = nums.reduce((acc, n) => acc + n, 0);
// 6

🔹 4. Transformation Methods

✅ concat()

Merges arrays

let a = [1,2];
let b = [3,4];
let result = a.concat(b); // [1,2,3,4]

✅ slice()

Returns shallow copy

let arr = [1,2,3,4];
arr.slice(1,3); // [2,3]

✅ flat()

Flattens nested arrays

let arr = [1, [2, [3]]];
arr.flat(2); // [1,2,3]

🔹 5. Search / Find Methods

✅ indexOf()

Returns first index

let arr = [10, 20, 30];
arr.indexOf(20); // 1

✅ includes()

Checks existence

arr.includes(30); // true

✅ find()

Returns first matching element

let users = [{id:1}, {id:2}];
let user = users.find(u => u.id === 2);

✅ findIndex()

Returns index of matching element

users.findIndex(u => u.id === 2); // 1

🔹 6. Utility Methods

✅ sort()

Sorts array (mutates original)

let arr = [3,1,2];
arr.sort(); // [1,2,3]

⚠️ For numbers:

arr.sort((a,b) => a - b);

✅ reverse()

Reverses array

arr.reverse();

✅ join()

Converts to string with separator

let arr = ["a", "b", "c"];
arr.join("-"); // "a-b-c"

15 JavaScript Array Programs with Solutions

1. Find Largest Number in Array

Solution

const numbers = [10, 45, 2, 99, 23];

const largest = Math.max(...numbers);

console.log(largest);

Output

99

2. Find Smallest Number in Array

Solution

const numbers = [10, 45, 2, 99, 23];

const smallest = Math.min(...numbers);

console.log(smallest);

Output

2

3. Sum of Array Elements

Solution

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

const sum = arr.reduce((total, num) => total + num, 0);

console.log(sum);

Output

15

4. Find Even Numbers

Solution

const numbers = [1, 2, 3, 4, 5, 6];

const even = numbers.filter(num => num % 2 === 0);

console.log(even);

Output

[2, 4, 6]

5. Find Odd Numbers

Solution

const numbers = [1, 2, 3, 4, 5, 6];

const odd = numbers.filter(num => num % 2 !== 0);

console.log(odd);

Output

[1, 3, 5]

6. Reverse an Array

Solution

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

const reversed = arr.reverse();

console.log(reversed);

Output

[5, 4, 3, 2, 1]

7. Remove Duplicate Elements

Solution

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

const unique = [...new Set(arr)];

console.log(unique);

Output

[1, 2, 3, 4, 5]

8. Sort Array in Ascending Order

Solution

const numbers = [40, 5, 100, 25];

numbers.sort((a, b) => a - b);

console.log(numbers);

Output

[5, 25, 40, 100]

9. Sort Array in Descending Order

Solution

const numbers = [40, 5, 100, 25];

numbers.sort((a, b) => b - a);

console.log(numbers);

Output

[100, 40, 25, 5]

10. Find Maximum and Minimum Together

Solution

const arr = [10, 20, 5, 90, 30];

const max = Math.max(...arr);
const min = Math.min(...arr);

console.log("Max:", max);
console.log("Min:", min);

Output

Max: 90
Min: 5

11. Merge Two Arrays

Solution

const arr1 = [1, 2, 3];
const arr2 = [4, 5, 6];

const merged = [...arr1, ...arr2];

console.log(merged);

Output

[1, 2, 3, 4, 5, 6]

12. Check if Element Exists

Solution

const fruits = ["apple", "banana", "mango"];

console.log(fruits.includes("banana"));
console.log(fruits.includes("orange"));

Output

true
false

13. Find Index of Element

Solution

const numbers = [10, 20, 30, 40];

const index = numbers.indexOf(30);

console.log(index);

Output

2

14. Convert Array to String

Solution

const fruits = ["apple", "banana", "mango"];

const result = fruits.join(", ");

console.log(result);

Output

apple, banana, mango

15. Find Second Largest Number

Solution

const arr = [10, 50, 20, 80, 60];

const sorted = [...arr].sort((a, b) => b - a);

console.log(sorted[1]);

Output

60

Bonus Program — Flatten Nested Array

Solution

const arr = [1, [2, 3], [4, [5, 6]]];

const flatArray = arr.flat(2);

console.log(flatArray);

Output

[1, 2, 3, 4, 5, 6]

Topics Covered

These programs cover:

  • map()
  • filter()
  • reduce()
  • sort()
  • includes()
  • indexOf()
  • join()
  • Spread operator
  • Set
  • Array manipulation
  • Searching
  • Sorting
  • Flattening arrays

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