Duck Punch - jQuery unique()

This is just trying out the idea of duck punching with jQuery by Paul Irish. http://paulirish.com/2010/duck-punching-with-jquery/

HTML

<div id="u"></div>

JavaScript

/**
  * This is just trying out the idea of duck punching with jQuery by Paul Irish.
  * You can read all about it here:
  * http://paulirish.com/2010/duck-punching-with-jquery/
  * Override jQuery's unique() to have it work with non-DOMElements as well
  */
(function($){
    var _old = $.unique;
    $.unique = function(arr){
        // do the default behavior only if we got an array of elements
        if (!!arr[0].nodeType){
            return _old.apply(this,arguments);
        } else {
            // reduce the array to contain no dupes via grep/inArray
            return $.grep(arr,function(v,k){
                return $.inArray(v,arr) === k;
            });
        }
    };
})(jQuery);
$(document).ready(function () {
    var x = ['a', 'b', 1, 'a', 2, 'c', 'd', 1, 'c', 'b', 3, 'a', 2, 1],
        y = $.unique(x);
    $('#u').html(y.join(', '));
});