javascript 返回数组中不重复的元素

这是实现结构伪类type-of-type的部分代码： 

<script type="text/javascript">
var ret= ["span","span","strong","span","b"]
var norepeat = function(array){
var set = array.join(",")+",";
while(array.length){
var el = array.shift();
set = set.replace(el+",","");
if(set.indexOf(el+",") != -1){
set = set.replace(new RegExp(el+",","g"),"");
array = set.replace(/,$/g,"").split(",");
}else{
set = el+","+set;
}
}
return set.replace(/,$/g,"").split(",")
}
alert(norepeat(ret))//最后返回b,strong
</script>

觉得效果不高，向无忧高手求救。下面是客服果果的(好强大的正则替换啊)： 

<script language="javascript">
var ret= ["span","span","strong","span","b"];
var norepeat=function (x) {
var y='c0cb5f0fcf239ab3d9c1fcd31fff1efc';
return x.sort().join(y).replace(RegExp('(.*('+y+'|$))\1+','g'),'').split(y);
};
alert(norepeat(ret));
</script>

abcdreamer 的实现（此实现能过滤非纯字符串数组里的重复，我比较喜欢）：

<script language="javascript">
var a = ["span","span","strong","span","b"];
function norepeat(a) {
var i = a.length, j, b;
while (i--) {
j = i;
b = false;
while (j--) {
if (a[i] === a[j]) {
a.splice(j, 1);
i--;
b = true;
}
}
if (b) a.splice(i, 1);
}
return a;
}
alert(norepeat(a));
</script>

哪位高手有更好的实现，请告诉我一声！ 
看来有些人不明白norepeat函数与unique函数的区别，norepeat是去除数组中重复的元素，如果数组中有两个a，则去除这两个，unique则会去除其中之一。下面是unique函数的实现： 

<script language="javascript">
Array.prototype.inArray = function(el){
for (var i=0,n=this.length;i<n;i++ )
if(this[i]===el)return true;
return false;
}
Array.prototype.unique = function() {
var i = 0, n = this.length,ret = [];
for (; i < n; i++)
if (!ret.inArray(this[i])) ret.push(this[i]);
return ret;
};
var ret= ["span","span","strong","span","b"]
alert(ret.unique()) //返回"span","strong","b"
</script>