Array.prototype.unique = function () {

    var res = [], hash = {};

    for (var i = 0, elem; (elem = this[i]) != null; i++) {

        if (!hash[elem]) {

            res.push(elem);

            hash[elem] = true;

        }

    }

    return res;

}

var arr = new Array(1, 3, 4, 5, 3);

arr = arr.unique();

alert(arr.join(","))  //输出1,3,4,5