To determine whether the date can be query across the month JS code _javascript skills

function Checkdate (startdate, EndDate, NUM, flag) {if (StartDate = null | | enddate = NULL) {POPWIN.I 
      NFO (' Hint ', ' date cannot be empty ');   
    return false; 
      } if (StartDate = = ' | | | enddate = = ') {popwin.info (' Prompt ', ' Enter query Date ');   
    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 (' hint ', ' due date cannot be less than start date ');   
    return false; 
    //Gets the date after num days var currentdate = new Date (); 
     
    Currentdate.setdate (currentdate.getdate () + num); 
      if (End_date > CurrentDate) {popwin.info (' hint ', ' due date cannot be greater than ' + num + ' days after Date ');  
    return false; ///Determine whether to query across the month if (flag = False) {if (Start_date.getmonth ()!= end_date.getmonth ()) {POPWI 
        N.info (' Hint ', ' the query does not support cross-month query '); Return False  } 
    } 
  }