每三位加小数点

<script type="text/javascript">

 String.prototype.format = function(){
        return this.replace(/\d(?=(?:\d{3})+\b)/g,function(v) {
            return v + ',';
        });
    }
    var a = 76884526;
    alert(a.toString().format()); //return 67,884,526.88
	</script>