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This feature is well established and works across many devices and browser versions. Its been available across browsers since 2020 ..
var new_array = arr.flatMap(function callback(currentValue[, index[, array]]) {
// new_array
}[, thisArg])
callback, :
currentValue.
index.
array.
thisArg this callback.
, callback "" 1.
Array.prototype.map() callback . flatMap map flat depth 1.
map flatMaplet arr1 = [1, 2, 3, 4];
arr1.map((x) => [x * 2]);
// [[2], [4], [6], [8]]
arr1.flatMap((x) => [x * 2]);
// [2, 4, 6, 8]
//
arr1.flatMap((x) => [[x * 2]]);
// [[2], [4], [6], [8]]
map, flatMap .
.
let arr1 = ["it's Sunny in", "", "California"];
arr1.map((x) => x.split(" "));
// [["it's","Sunny","in"],[""],["California"]]
arr1.flatMap((x) => x.split(" "));
// ["it's","Sunny","in", "", "California"]
, .
//=> [1, 2, 3, 4, 5, 6, 7, 8, 9]
reduce and concatvar arr1 = [1, 2, 3, 4];
arr1.flatMap((x) => [x * 2]);
// is equivalent to
arr1.reduce((acc, x) => acc.concat([x * 2]), []);
// [2, 4, 6, 8]
//=> [1, 2, 3, 4, 5, 6, 7, 8, 9]
| Specification |
|---|
| ECMAScript 2027 LanguageSpecification # sec-array.prototype.flatmap |
This page was last modified on 24 . 2025 . by MDN contributors.
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