flat()

ES2019+

Creates a new array with all sub-array elements concatenated into it recursively up to the specified depth.

Syntax

array.flat(depth)

depth number optional

The depth level specifying how deep a nested array structure should be flattened (default: 1)

Array

A new array with the sub-array elements concatenated

JavaScript

const nested = [1, [2, [3, [4]]]];
console.log(nested.flat());
console.log(nested.flat(2));

Output:

// [1, 2, [3, [4]]] [1, 2, 3, [4]]