js 四舍五入 保留两位

            keepTwoDecimalFull(num) {
                var result = parseFloat(num);
                if (isNaN(result)) {
                    alert('传递参数错误，请检查！');
                    return false;
                }
                result = Math.round(num * 100) / 100;
                var s_x = result.toString();
                var pos_decimal = s_x.indexOf('.');
                if (pos_decimal < 0) {
                    pos_decimal = s_x.length;
                    s_x += '.';
                }
                while (s_x.length <= pos_decimal + 2) {
                    s_x += '0';
                }
                return s_x;
            },