code: function() {
      var result = this.unique();
  
      for (var i = 0; i < arguments.length; i++) {
        var array = arguments[i];
        for (var j = 0; j < array.length; j++) {
          if (result.indexOf(array[j]) < 0) {
            result.push(array[j]);
          }
        }
      }
  
      return result;
    }
docs: Returns an array that is the [union](http://en.wikipedia.org/wiki/Union_%28set_theory%29)
  of the array and the input array(s).
  
  @function Array#union
  @param {...Array} arrays - A variable number of arrays.
  @returns {Array} The new array containing every distinct element found in the arrays.
  
  @example
  [1, 2, 3].union([2, 3, 4, 5]);
  // -> [1, 2, 3, 4, 5]
  
  [1, 2].union([4, 2], [2, 1]);
  // -> [1, 2, 4]