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].

flattenRecursive.js

/*
  Example of a flatten array method using recursion. If the original array is
  large do NOT use this funtion. Too much memory is used off the stack.
*/

let array =  [[1,2,[3]],4];
let newArray = flattenRecursive(array);

function flattenRecursive(array, results = []) {
  for (let i = 0; i < array.length; i++) {
      if (Array.isArray(array[i])) {
        flattenRecursive(array[i], results); // called until the inner most array is reached
      } else {
        results.push(array[i]);
      }
  }
  return results;
}