JavaScript (ES2026) reference · Array Methods

JavaScript Array flatMap() Method

Map each element with a function, then flatten the result one level. Useful when one element becomes several.

JavaScript (ES2026) Since ES2019

Syntax

array.flatMap(callbackFn, thisArg)

Parameter	Description
`callbackFn`	Called for each element with `(element, index, array)`.

A new array.

Split into wordsTry it yourself

const sentences = ["hello world", "good morning"];
console.log(sentences.flatMap((s) => s.split(" ")));

Output

[ 'hello', 'world', 'good', 'morning' ]

Filter and duplicate in one passTry it yourself

const nums = [1, 2, 3, 4];
console.log(nums.flatMap((n) => (n % 2 ? [n, n] : [])));

Output

[ 1, 1, 3, 3 ]

Version	Change
JavaScript ES2019	Added

array.map() · Return a new array with the results of calling a function on every element. The original array is unchanged.
array.flat() · Return a new array with nested arrays flattened into it, one level deep by default or to a given depth.
array.filter() · Return a new array with only the elements that pass a test function. The original array is not changed.
JavaScript Arrays · tutorial
JavaScript Array Methods · tutorial