1  /*!
 2   * arr-flatten <https://github.com/jonschlinkert/arr-flatten>
 3   *
 4   * Copyright (c) 2014-2017, Jon Schlinkert.
 5   * Released under the MIT License.
 6   */
 7  
 8  'use strict';
 9  
10  module.exports = function (arr) {
11    return flat(arr, []);
12  };
13  
14  function flat(arr, res) {
15    var i = 0, cur;
16    var len = arr.length;
17    for (; i < len; i++) {
18      cur = arr[i];
19      Array.isArray(cur) ? flat(cur, res) : res.push(cur);
20    }
21    return res;
22  }