判断日期是否能跨月查询的js代码

function checkDate(startDate, endDate, num, flag) {          if(startDate == null || endDate == null) {       popwin.info('提示','日期不可为空');       return false;       }      if(startDate == '' || endDate == '') {       popwin.info('提示','请输入查询日期');       return false;       }          var start_date = startDate + " 00:00";     var end_date = endDate + " 00:00";     start_date = new Date(start_date.replace(/-/g, "/"));     end_date = new Date(end_date.replace(/-/g, "/"));     if(start_date > end_date){       popwin.info('提示','截止日期不能小于起始日期');       return false;       }          // 获取num天以后的日期       var currentDate = new Date();     currentDate.setDate(currentDate.getDate() + num);          if(end_date > currentDate) {       popwin.info('提示','截止日期不能大于' + num + '天之后的日期');       return false;      }          // 判断是否跨月查询     if(flag == false) {       if(start_date.getMonth() != end_date.getMonth()) {         popwin.info('提示','该查询不支持跨月查询');         return false;        }     }   }