code: function() {
      var result = [];
  
      for (var i = 0; i < this.length; i++) {
        var value = this[i];
        if (Array.isArray(value)) {
          for (var j = 0; j < value.length; j++) {
            result.push(value[j]);
          }
        } else {
          result.push(value);
        }
      }
  
      return result;
    }
docs: Flattens a nested array a single level.
  
  @function Array#flatten
  @returns {Array} The new flattened array.
  
  @example
  [1, [2, 3, [4]], 5].flatten();
  // -> [1, 2, 3, [4], 5]