Tech

Javascript Array Methods cheat sheet

Javascript Array Methods cheat sheet. Explore our ultimate quick reference for Javascript Array Methods.

Search in this cheat sheet:

Welcome to this comprehensive cheat sheet covering 43 JavaScript array methods, categorized for easy reference. Whether you're a beginner or an experienced developer, you'll find clear explanations and examples to enhance your coding efficiency. For further reading and detailed documentation, visit the MDN Web Docs. Happy coding!

Creation Methods

from()

Creates a new Array instance from an array-like or iterable object.

const set = new Set(['foo', 'bar', 'baz']);
const array = Array.from(set);
console.log(array); // ["foo", "bar", "baz"]

fromAsync()

Creates a new Array instance from an array-like or iterable object asynchronously.

async function example() {
    const array = await Array.fromAsync(async function*() {
        yield 'foo';
        yield 'bar';
        yield 'baz';
    }());
    console.log(array); // ["foo", "bar", "baz"]
}
example();

isArray()

Checks if the given value is an array.

console.log(Array.isArray([1, 2, 3])); // true
console.log(Array.isArray('not an array')); // false

of()

Creates a new Array instance with a variable number of arguments.

const array = Array.of(1, 2, 3);
console.log(array); // [1, 2, 3]

Accessor Methods

Array[@@iterator]()

Returns a new Array Iterator object that contains the values for each index.

const array = ['a', 'b', 'c'];
const iterator = array[Symbol.iterator]();
console.log(iterator.next().value); // "a"

at()

Returns the element at the given index, allowing for positive and negative integers.

const array = [1, 2, 3, 4];
console.log(array.at(-1)); // 4

entries()

Returns a new Array Iterator object that contains the key/value pairs for each index.

const array = ['a', 'b', 'c'];
const iterator = array.entries();
for (let entry of iterator) {
  console.log(entry);
}
// [0, "a"]
// [1, "b"]
// [2, "c"]

includes()

Determines whether an array includes a certain value.

const array = [1, 2, 3];
console.log(array.includes(2)); // true
console.log(array.includes(4)); // false

indexOf()

Returns the first index at which a given element can be found.

const array = [1, 2, 3, 1, 2, 3];
console.log(array.indexOf(2)); // 1
console.log(array.indexOf(4)); // -1

join()

Joins all elements of an array into a string.

const array = ['a', 'b', 'c'];
console.log(array.join('-')); // "a-b-c"

keys()

Returns a new Array Iterator object that contains the keys for each index.

const array = ['a', 'b', 'c'];
const iterator = array.keys();
for (let key of iterator) {
  console.log(key);
}
// 0
// 1
// 2

lastIndexOf()

Returns the last index at which a given element can be found.

const array = [1, 2, 3, 1, 2, 3];
console.log(array.lastIndexOf(2)); // 4
console.log(array.lastIndexOf(4)); // -1

toString()

Returns a string representing the elements of the array.

const array = [1, 2, 'a', 'b'];
console.log(array.toString()); // "1,2,a,b"

toLocaleString()

Returns a localized string representing the elements of the array.

const array = [1, 'a', new Date(Date.UTC(2021, 1, 1, 0, 0, 0))];
console.log(array.toLocaleString('en', { timeZone: 'UTC' }));
// "1,a,1/1/2021, 12:00:00 AM"

values()

Returns a new Array Iterator object that contains the values for each index.

const array = ['a', 'b', 'c'];
const iterator = array.values();
for (let value of iterator) {
  console.log(value);
}
// "a"
// "b"
// "c"

Mutator Methods

concat()

Merges two or more arrays into one new array.

const array1 = [1, 2];
const array2 = [3, 4];
const newArray = array1.concat(array2);
console.log(newArray); // [1, 2, 3, 4]

copyWithin()

Copies a part of the array to another location within the same array.

const array = [1, 2, 3, 4, 5];
array.copyWithin(0, 3);
console.log(array); // [4, 5, 3, 4, 5]

fill()

Fills all the elements of an array with a static value.

const array = [1, 2, 3, 4];
array.fill(0, 2);
console.log(array); // [1, 2, 0, 0]

pop()

Removes the last element from an array and returns that element.

const array = [1, 2, 3];
const lastElement = array.pop();
console.log(lastElement); // 3
console.log(array); // [1, 2]

push()

Adds one or more elements to the end of an array and returns the new length.

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

reverse()

Reverses the order of the elements in an array.

const array = [1, 2, 3];
array.reverse();
console.log(array); // [3, 2, 1]

shift()

Removes the first element from an array and returns that element.

const array = [1, 2, 3];
const firstElement = array.shift();
console.log(firstElement); // 1
console.log(array); // [2, 3]

slice()

Returns a shallow copy of a portion of an array into a new array.

const array = [1, 2, 3, 4];
const newArray = array.slice(1, 3);
console.log(newArray); // [2, 3]

sort()

Sorts the elements of an array in place and returns the array.

const array = [3, 1, 4, 1, 5];
array.sort();
console.log(array); // [1, 1, 3, 4, 5]

splice()

Changes the contents of an array by removing or replacing existing elements and/or adding new elements.

const array = [1, 2, 3, 4];
array.splice(1, 2, 'a', 'b');
console.log(array); // [1, "a", "b", 4]

unshift()

Adds one or more elements to the beginning of an array and returns the new length.

const array = [2, 3];
const newLength = array.unshift(1);
console.log(newLength); // 3
console.log(array); // [1, 2, 3]

with()

Creates a new array with a modified value at the specified index.

const array = [1, 2, 3];
const newArray = array.with(1, 'a');
console.log(newArray); // [1, "a", 3]

Iteration Methods

every()

Tests whether all elements in the array pass the provided function.

const array = [1, 2, 3, 4];
const allBelowFive = array.every(num => num < 5);
console.log(allBelowFive); // true

filter()

Creates a new array with all elements that pass the provided function.

const array = [1, 2, 3, 4];
const filteredArray = array.filter(num => num > 2);
console.log(filteredArray); // [3, 4]

find()

Returns the first element that passes the provided function.

const array = [1, 2, 3, 4];
const foundElement = array.find(num => num > 2);
console.log(foundElement); // 3

findIndex()

Returns the index of the first element that passes the provided function.

const array = [1, 2, 3, 4];
const foundIndex = array.findIndex(num => num > 2);
console.log(foundIndex); // 2

findLast()

Returns the last element that passes the provided function.

const array = [1, 2, 3, 4];
const foundLastElement = array.findLast(num => num > 2);
console.log(foundLastElement); // 4

findLastIndex()

Returns the index of the last element that passes the provided function.


const array = [1, 2, 3, 4];
const foundLastIndex = array.findLastIndex(num => num > 2);
console.log(foundLastIndex); // 3

flat()

Creates a new array with all sub-array elements concatenated into it.

const array = [1, [2, 3], [4, [5]]];
const flatArray = array.flat(2);
console.log(flatArray); // [1, 2, 3, 4, 5]

flatMap()

Maps each element using a mapping function, then flattens the result into a new array.

const array = [1, 2, 3];
const flatMappedArray = array.flatMap(num => [num, num * 2]);
console.log(flatMappedArray); // [1, 2, 2, 4, 3, 6]

forEach()

Executes a provided function once for each array element.

const array = [1, 2, 3];
array.forEach(num => console.log(num * 2));
// 2
// 4
// 6

map()

Creates a new array with the results of calling a provided function on every element.

const array = [1, 2, 3];
const mappedArray = array.map(num => num * 2);
console.log(mappedArray); // [2, 4, 6]

reduce()

Executes a reducer function on each element, resulting in a single output value.

const array = [1, 2, 3, 4];
const sum = array.reduce((acc, num) => acc + num, 0);
console.log(sum); // 10

reduceRight()

Executes a reducer function on each element from right to left, resulting in a single output value.

const array = [1, 2, 3, 4];
const sum = array.reduceRight((acc, num) => acc + num, 0);
console.log(sum); // 10

some()

Tests whether at least one element in the array passes the provided function.

const array = [1, 2, 3, 4];
const hasEven = array.some(num => num % 2 === 0);
console.log(hasEven); // true

Transformation Methods

toReversed()

Returns a new array with the elements in reverse order.

const array = [1, 2, 3];
const reversedArray = array.toReversed();
console.log(reversedArray); // [3, 2, 1]

toSorted()

Returns a new array with the elements sorted.

const array = [3, 1, 4, 1, 5];
const sortedArray = array.toSorted();
console.log(sortedArray); // [1, 1, 3, 4, 5]

toSpliced()

Returns a new array with some elements removed/replaced and/or new elements added.

const array = [1, 2, 3, 4];
const splicedArray = array.toSpliced(1, 2, 'a', 'b');
console.log(splicedArray); // [1, "a", "b", 4]