Q:

Uncaught TypeError: Cannot read property of null

Hello im having trouble of fixing this error Uncaught TypeError: Cannot read property '2' of null. This is what i want to do, if i click to the day without event the #myModal will show but if i click the day with event the #delete modal will show. But my problem is when im clicking the day without event im getting an error of Uncaught TypeError: Cannot read property '2' of null. 

here's the ajax 
  dayClick: function(date, allDay, jsEvent, view) {
    var datee = date.format();
                 $.ajax({
                url:'getrecords.php',
                method:'POST',
                dataType: 'json',     
                data:{
                  "filter": 1,
                  "start": datee

                },
                success:function(data){
                var date = data[2];    

                if(date == datee){
                  $('#delete').modal('show');
                }
                else{
                  $('#myModal').modal('show');
                }

                }
              });

here's the php 
  if(isset($_POST['filter']))
   {
        $start = $_POST['start'];
         $select = mysqli_query($con,"SELECT * FROM appointment WHERE start = '$start'");     
        $check_user = mysqli_num_rows($select);
      $array = mysqli_fetch_row($select);  
      echo json_encode($array);   
   }

A:

This is most likely the result of the data being passed into your success callback being null. Accessing it like it is an array will then yield the type error you are seeing. Without know too much about your app, maybe try changing your logic to:
//your previous code then handle success like:           

        success:function(data){
            if (data === null) {
               $('#myModal').modal('show');
            } else {
               $('#delete').modal('show');
            }            
         }

