4 JavaScript Array methods you must know

JavaScript, Array, Cheatsheet · Jun 12, 2021

JavaScript arrays have a very robust API offering a plethora of amazing tools. Here are our top 4 JavaScript array methods every developer should know:


Array.prototype.map() creates a new array by applying the provided transformation to each element of the original array. The result is an array with the same length as the original array and elements transformed based on the provided function.

const arr = [1, 2, 3];
const double = x => x * 2;
arr.map(double); // [2, 4, 6]


Array.prototype.filter() creates a new array by using a filtering function to keep only elements that return true based on that function. The result is an array with equal or less than the original array's length, containing a subset of the same elements as the original array.

const arr = [1, 2, 3];
const isOdd = x => x % 2 === 1;
arr.filter(isOdd); // [1, 3]
JavaScript Array Methods


Array.prototype.reduce() creates an output value of any type depending on a reducer function and an initial value. The result can be of any type such as an integer, an object or an array, based on the reducer function provided.

const arr = [1, 2, 3];

const sum = (x, y) => x + y;
arr.reduce(sum, 0); // 6

const increment = (x, y) => [...x, x[x.length - 1] + y];
arr.reduce(increment, [0]); // [0, 1, 3, 6]


Array.prototype.find() returns the first element for which a matcher function returns true. The result is a single element from the original array.

const arr = [1, 2, 3];
const isOdd = x => x % 2 === 1;
arr.find(isOdd); // 1

Written by Angelos Chalaris

I'm Angelos Chalaris, a JavaScript software engineer, based in Athens, Greece. The best snippets from my coding adventures are published here to help others learn to code.

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