flattens a nested array of integers at any depth

flatten-nested-array.js

/**
 * flattenNested - Reduces an array of arbitrarily nested arrays of integers into a flat array of integers.
 * @param value {Array} - The array to flatten.
 * @param iterator {Array} - An array used for initializing or for iteration during recursion.
 * @returns {Array} - The flattened array, yay!
 */
function flattenNested(value, iterator = []) {
  // Add exit case straight away to help prevent stack overflow
  if (!value) return iterator;

  // Ensure that the value is an array before calling prototype methods on it
  for (item of value) {
    if (Array.isArray(item)) {
      // Flatten nested array using recursion
      flattenNested(item, iterator);
    } else {
      // Push the item onto the iterator
      iterator.push(item);
    }
  };
  return iterator;
}