<script type="text/javascript">

     function addDay(datetime, days) {

         var old_time = new Date(datetime.replace(/-/g, "/")); //替换字符，js不认2013-01-31,只认2013/01/31

         var fd = new Date(old_time.valueOf() + days * 24 * 60 * 60 * 1000); //日期加上指定的天数

         var new_time = fd.getFullYear() + "-";

         var month = fd.getMonth() + 1;

         if (month >= 10) {

             new_time += month + "-";

         } else {

             //在小于10的月份上补0

             new_time += "0" + month + "-";

         }

         if (fd.getDate() >= 10) {

             new_time += fd.getDate();

         } else {

             //在小于10的日期上补0

             new_time += "0" + fd.getDate();

         }

         return new_time; //输出格式：2013-01-02

     }

     alert(addDay("2013-11-12", 1)); //弹出值：2013-11-13

 </script>