"use strict";

type NestedArray<T> = NestedArray<T>[] | T[];

/**
 * Flattens an array which itself may contain arrays (which may contain arrays etc), into a single array,
 * eg. flattenNested([[0, [11, 12, [13]]], [2, 3], 4]) = [0, 11, 12, 13, 2, 3, 4].
 * @private
 * @param  {Array[]} array Input array.
 * @return {Array} Flattened array.
 */
export default function flattenNested<T>(array: NestedArray<T>): T[] {
  return flattenNestedLoop(array, []);
}

function flattenNestedLoop<T>(array: NestedArray<T>, result: T[]) {
  for (var i = 0; i < array.length; i++) {
    var value = array[i];
    if (Array.isArray(value)) {
      flattenNestedLoop(value, result);
    } else {
      result.push(value);
    }
  }
  return result;
}