千分位添加和去掉方法

//把千分位转换成数字
        function commafyback(num)
        {
            var x = num.split(',');
            return parseFloat(x.join(""));
        }
        //加千分位
        function comdify(n) {
            var re = /\d{1,3}(?=(\d{3})+$)/g;
            var n1 = n.replace(/^(\d+)((\.\d+)?)$/, function (s, s1, s2) {
                return s1.replace(re, "$&,") + s2;
            });

            return n1;
        }