grence's program note

function wl(s){document.write(s+"<br>");}
var normalNum='12345678987654321';
var kukuNum='134123142133894329AAA8539807831278187938';

function format1(num)...{
    num = num.toString();
    var re=/(-?\d+)(\d...{3})/;
    while(re.test(num))...{
  num=num.replace(re,"$1,$2");
    }
    return num;
}
wl('function');
wl(format1(normalNum));
wl(format1(kukuNum));

var re1 =/(\d...{1,3})(?=(\d{3})+[^\d])/g;
//(\d...{1,3}) 如果 1~3個數字後面跟著..(?=(\d{3})+[^\d]) 1組以上的(3個數字)，一直抓到非數字結尾..就抓出來

wl('re1='+re1);
wl(normalNum.replace(re1,"$1,"));//數字結尾就炸了。
wl(kukuNum.replace(re1,"$1,"));

var re2=/(\d...{1,3})(?=(\d{3})+(?:$|\.))/g;
wl('re2='+re2);
wl(normalNum.replace(re2,"$1,"));
wl(kukuNum.replace(re2,"$1,"));

var re3=/(\d...{1,3})(?=(\d{3})+(?:$|[^\d]))/g;
wl('re3='+re3);
wl(normalNum.replace(re3,"$1,"));
wl(kukuNum.replace(re3,"$1,"));