Removing duplicates in a javascript array

I was looking at this today and discovered grep.

$(function () {

    var myOriginalValues = [1, 3, 7, 3, 3, 9, 2];
    var res = [];

    $.each(myOriginalValues, function (i, el) {
        if ($.inArray(el, res) === -1) res.push(el);
    });

    // Now a grep version
    var grepVersion = function(arr){
        return $.grep(arr,function(v,k){
            return $.inArray(v, arr) === k;
        })
    };

    var arr = ['tree',2,4,5,4,1,1,3,3,5, 'tree', 'hat']
    var x = grepVersion(arr);

});