function splitNum(str){
if(!str){
return "";
}
var strArr = (str+"").split("").reverse().join("").replace(/(\d{3})/g,"$1,").split("").reverse();
strArr[0] == "," && (strArr[0] = "");
return strArr.join("");
3位分割，传入需要分割的数字即可
原文：http://www.cnblogs.com/byit/p/5447399.html