用javascript如何删除一个数组中的重复元素

<script type="text/javascript">

Array.prototype.unique = function()

{

var a = {};//一个空的数组;

for(var i=0; i<this.length; i++)

{

if(typeof a[this[i]] == "undefined")

a[this[i]] = 1;

}

this.length = 0;

for(var i in a)

this[this.length] = i;

return this;

}

var a = [1,2,4,12,5,3,5,4,8,5,2,8,8,1,5];

alert(a +"/n"+ a.unique());

</script>