`Array.prototype.flat()`

Returns a new array with sub-array elements flattened to the specified depth.

Since ES2019 Spec ↗

Syntax

arr.flat(depth)

Name	Type	Required	Description
`depth`	`number`	No	How many levels of nesting to flatten. Defaults to 1. Use Infinity to flatten fully.

Array — A new flattened array.

console.log([1, [2, [3]]].flat());

Output

[ 1, 2, [ 3 ] ]

console.log([1, [2, [3, [4]]]].flat(Infinity));

Output

[ 1, 2, 3, 4 ]

Does not mutate the original array. Also removes empty slots in sparse arrays. For mapping then flattening one level, `flatMap` is more efficient.