Write some code, that will flatten an array of arbitrarily nested arrays of integers into a flat array of integers. e.g. [[1,2,[3]],4] -> [1,2,3,4].

arrayFlatten

flatten = (array, result) => {
	if(array.length === 0) return result;
  let head = array[0];
  let rest = array.slice(1);
	
  if (Array.isArray(head)) {
    return flatten(head.concat(rest), result);
  };
  result.push(head);
  return flatten(rest, result);
};

console.log(flatten([[1,2,[3]], 4], [])); // [1, 2, 3, 4]