Per chi cercava la soluzione....


<HEAD>

<SCRIPT LANGUAGE="JavaScript">


<!-- Begin
function replaceChars(entry) {
out = "."; // replace this
add = ","; // with this
temp = "" + entry; // temporary holder

while (temp.indexOf(out)>-1) {
pos= temp.indexOf(out);
temp = "" + (temp.substring(0, pos) + add +
temp.substring((pos + out.length), temp.length));
}
document.subform.text.value = temp;
}
// End -->
</script>
</HEAD>


<BODY>

<center>
<form name="subform">

<input type=text name=text size=40 value="abcdabcd. . , ,">


<input type=button name=action value="Done!" onClick="replaceChars(document.subform.text.value) ;">
</form>
</center>