In JavaScript, arrays are one of the most fundamental data structures. Understanding array methods allows you to write cleaner, more efficient, and more maintainable code.

This guide covers the most important JavaScript array methods with practical examples.

1. Adding and Removing Elements

These are the most basic operations when working with arrays.

push() – Add to the end

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

pop() – Remove from the end

arr.pop(); // [1, 2]

unshift() – Add to the beginning

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

shift() – Remove from the beginning

arr.shift(); // [1, 2]

👉 Commonly used when implementing stacks or queues.

2. Iterating and Transforming Arrays

These are the most important methods in real-world development.

map() – Create a new array

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

filter() – Filter elements

let even = numbers.filter(x => x % 2 === 0);
// [2]

reduce() – Aggregate values

let sum = numbers.reduce((a, b) => a + b, 0);
// 6

forEach() – Iterate through elements

numbers.forEach(x => console.log(x));

👉 The most important trio: map – filter – reduce

3. Searching in Arrays

find() – Return the first matching element

numbers.find(x => x > 1); // 2

findIndex() – Return index

numbers.findIndex(x => x > 1); // 1

includes() – Check existence

numbers.includes(2); // true

indexOf() – Find position

numbers.indexOf(2); // 1

4. Array Manipulation

slice() – Extract a portion (non-mutating)

numbers.slice(0, 2);

splice() – Modify the array (mutating)

numbers.splice(1, 1); // remove 1 element

concat() – Merge arrays

numbers.concat([4, 5]);

5. Sorting and Reversing

sort()

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

reverse()

numbers.reverse();

6. Converting Arrays

join()

numbers.join(", "); // "1, 2, 3"

toString()

numbers.toString();

7. Modern Methods (ES6+)

flat()

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

flatMap()

[1, 2].flatMap(x => [x, x * 2]);

at()

numbers.at(-1); // last element

When Should You Use Each Method?

• map() → Transform data
  

• filter() → Select specific items
  

• reduce() → Calculate totals or summaries
  

• find() → Get a single matching item
  

• forEach() → Loop without returning data