JS实现数字格式化输出，比如输入999999999，输出9,999,999,999
splitNum:function(n){
var b=parseInt(n).toString();
var len=b.length;
if(len<=3){return b;}
var r=len%3;
return r>0?b.slice(0,r)+","+b.slice(r,len).match(/\d{3}/g).join(","):b.slice(r,len).match(/\d{3}/g).join(",");
}
