<script>
function replace(){
var str = "604134a,604135b,604134c,604134a,604134d,604134e,604134c,604134d,604134e,";
var arr = str.split(",");
var newstr = new String();
for (i =0; i < arr.length; i++)
{
if (newstr.indexOf(arr[i]) < 0 )
newstr += arr[i] + ",";
}
alert(newstr);
}
</script>
<input type=button onclick="replace()" value="Click me">