Create a function that takes an array. This array can have all kinds of primitives, even other arrays. The function should return a single, flat, one-dimensional, array with all elements. Here are the conditions:

1. If the item is an Array, include each item in it and the following still apply:
2. If the item is a Primitive, include it as is.

Examples

flatten_array([1, 2, [3, [4, 5], 6], 7, 8]) ➞ [1, 2, 3, 4, 5, 6, 7, 8]

flatten_array([1]) ➞ [1]

flatten_array([]) ➞ []

Notes

If no input is given it should return an empty array: [].