清除一个数组里面重复的元素

        var arr1 = [1, 3, 2, 3];
        var arr2 = [];
        for (var i = 0; i < arr1.length; i++) {
            if (arr2.indexOf(arr1[i]) < 0) {
                arr2.push(arr1[i]);
            }
        }
        document.write(arr2);