code: function stringifyArray(arr, prefix) {
    var ret = [];
    if (!prefix) throw new TypeError('stringify expects an object');
    for (var i = 0; i < arr.length; i++) {
      ret.push(stringify(arr[i], prefix + '[]'));
    }
    return ret.join('&');
  }
docs: Stringify the given `arr`.
  
  @param {Array} arr
  @param {String} prefix
  @return {String}
  @api private