javascript正则表达式显示千分位货币

<script language="JavaScript">   
n="1279834847944074100465236.33"  
re=/(\d{1,3})(?=(\d{3})+(?:$|\.))/g   
n1=n.replace(re,"$1,")   
alert(n+"\r\n"+n1)   
document.write(n+"\r\n"+n1);  
</script>