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; ???}