1. Web
  2. JavaScript
  3. Reference
  4. Standard built-in objects
  5. Array
  6. flat()

Array.prototype.flat()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since January 2020.

The flat() method of Array instances creates a new array with all sub-array elements concatenated into it recursively up to the specified depth.

Try it

const arr1 = [0, 1, 2, [3, 4]];

console.log(arr1.flat());
// expected output: Array [0, 1, 2, 3, 4]

const arr2 = [0, 1, [2, [3, [4, 5]]]];

console.log(arr2.flat());
// expected output: Array [0, 1, 2, Array [3, Array [4, 5]]]

console.log(arr2.flat(2));
// expected output: Array [0, 1, 2, 3, Array [4, 5]]

console.log(arr2.flat(Infinity));
// expected output: Array [0, 1, 2, 3, 4, 5]

Syntax