JavaScript加减计算方法和显示千分位

        Math.formatFloat = function (f, digit) {

            var m = Math.pow(10, digit);

            return parseInt(f * m, 10) / m;

        };

使用：var fee = Math.formatFloat(Number(a) + Number(b), 8).toFixed(2);

        function formatThousand(num) {

            num = num + "";

            var re = /(-?\d+)(\d{3})/;

            while (re.test(num)) {

                num = num.replace(re, "$1,$2");

            }

            return num;

        }

使用：formatThousand(fee);