Flatten nested arrays Recursion Challenge

Given an array that may contain nested arrays at any depth, return a new single-level array with all values preserved in order.

Function Signature

flatten(array)

Parameters

• array — an array that may contain values or nested arrays at arbitrary depth.

Output

Return a flat array containing all non-array values from the input.

Constraints

• The function must use recursion.
• Do not use Array.prototype.flat.
• The function should accept exactly one argument.

Examples

flatten([[1], [2, 3], [[4]], 5])       → [1, 2, 3, 4, 5]
flatten([3, [0, [34, [7, [18]]]]])     → [3, 0, 34, 7, 18]
flatten([[1], [2, [], 3], [], [[4]], 5]) → [1, 2, 3, 4, 5]