check บังคับใส่ข้อมูลใน datatable form alert แต่หน้าแรก หน้าอื่นไม่ alert ต้องทำยังไงคะ

<table id="example1" >
<tr>
    <td style="width: 15%"  class="text-center" >
  <input type="checkbox" name="check[]" id="check<?php echo $p; ?>" value="<?php echo $id; ?>"  
  <? if($chk != ''){ ?> checked  <? } if($user == 'Y' ) {?> disabled <? } ?> /></td>
<td style="width: 27%" >
<input type="text"  name="mass[<?=$id;?>]" id="mass<?php echo $p; ?>" value="<?php echo $mass1; ?>"
 <?php if($user == 'Y') { ?> disabled <? } ?> disabled   /> </td>
</tr>
</table>
<button type="submit"   onclick="return check_sub()">
<script>     
            $(document).on('click', 'input[name="check[]"]', function () {
                var checked = $(this).prop('checked');// true or false
                if (checked) {
                    $(this).parents('tr').find('td input[type="text"]').removeAttr('disabled');		
						
                }else {
                    $(this).parents('tr').find('td input[type="text"]').attr('disabled', 'disabled');
                }
            });
 
 </script>
<script>
  $(function () {
	 // alert($("#num").val());
    $("#example1").DataTable({
      "responsive": true, "lengthChange": false, "autoWidth": false,
      "buttons": ["copy", "excel", "pdf"],
	  "columnDefs": [{
		  "orderable": false,
		  "targets": [1,2,3]
		  }]
    }).buttons().container().appendTo('#example1_wrapper .col-md-6:eq(0)');
	
var table = $('#example1').DataTable();
$("form").on('submit', function(e){
   var form = this;
      var params = table.$('input,select,textarea').serializeArray();
      $.each(params, function(){     
         if(!$.contains(document, this)){
            $(form).append(
               $('<input>')
                  .attr('type', 'hidden')
                  .attr('name', this.name)
                  .val(this.value)
            );
         } 
		 
      });  
 	  
});	


    $('#example2').DataTable({
      "paging": true,
      "lengthChange": false,
      "searching": false,
      "ordering": true,
      "info": true,
      "autoWidth": false,
      "responsive": true,
	  
    });
  });

</script>
function check_sub(){
var num = document.getElementById('num').value;	
for(i=1;i<=11;i++){
var error = true;
	if(document.getElementById('check'+i).checked==true)
	{		
        	
		var data = "mass"+i;
		var box=document.getElementById(data).value;
		if(box == ""){
		  alert(data);
		  return false;
		} 
	} 
}
}