function getOffsetDays(startDate, endDate){

   var startDateArr = startDate.split("-");

   var checkStartDate = new Date();

   checkStartDate.setFullYear(startDateArr[0], startDateArr[1], startDateArr[2]);

   var endDateArr = endDate.split("-");

   var checkEndDate = new Date();

   checkEndDate.setFullYear(endDateArr[0], endDateArr[1], endDateArr[2]);

   var days = (checkEndDate.getTime() - checkStartDate.getTime())/ 3600000 / 24;

   if(startDateArr[0]!=endDateArr[0]){

     flag = true;

   }

   return days;

}

//调用

$(function(){

  var  offsetDays = getOffsetDays("2017-12-01","2017-12-01");

  console.log("相隔天数："+offsetDays);

));