js添加千位分隔符

function thousandBitSeparator(num){
    　　var re=/\d{1,3}(?=(\d{3})+$)/g;
    　　var n1=num.toString().replace(/^(\d+)((\.\d+)?)$/,function(s,s1,s2){return s1.replace(re,"$&,")+s2;});
    　　return n1;
    }