//四舍五入保留2位小数（若第二位小数为0，则保留一位小数）

 function keepTwoDecimal(num) {

   var result = parseFloat(num);

   if (isNaN(result)) {

     console.error('参数非数值，无法四舍五入保留两位小数！');

     return false;

   }

   result = Math.round(num * 100) / 100;

   return result;

 }

 //四舍五入保留2位小数（不够位数，则用0替补）

 function keepTwoDecimalFull(num) {

   var result = parseFloat(num);

   if (isNaN(result)) {

     console.error('参数非数值，无法四舍五入保留两位小数！');

     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;

 }