Array.prototype.flat()

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

The flat() method is a copying method. It does not alter this but instead returns a shallow copy that contains the same elements as the ones from the original array.

The flat() method removes empty slots if the array being flattened is sparse. For example, if depth is 1, both empty slots in the root array and in the first level of nested arrays are ignored, but empty slots in further nested arrays are preserved with the arrays themselves.

Syntax example: flat()