Datatables handle null ajax response?

Question

This is my datatable code:

table = $('#datatable-buttons').DataTable({
          lengthChange: false,
          pageLength: 25,
          order: [ 0, 'desc' ],
          //buttons: ['copy', 'excel', 'pdf', 'colvis']
          columns: [
            { data: "sample_lab_ref" },
            { data: "sample_client_ref" },
            { data: "sample_client_ref2" },
            { data: "sample_client_ref3" },
            { data: "sample_date" },
            { data: "report_date" },
            { data: "test_parameter_name" },
            { data: "test_parameter_sop" },
            { data: "test_technique_name" },
            { data: "test_value_text" },
            { data: "test_units" }
          ],
          columnDefs: [
            {
              targets: [4, 5],
              visible: false,
              searchable: false
            }
          ],
          ajax: {
            url: "/assets/ajax/test_data_ajax_handler.php",
            type: "POST",
            data: {
              action: "getTestData",
              user_data: '<?=json_encode($userData)?>'
            }
          },
          buttons: {
              buttons: [
                  { extend: 'copy', className: 'btn-info' },
                  { extend: 'pdf', className: 'btn-danger' },
                  { 
                      extend: 'csv', 
                      className: 'btn-success', 
                      text: 'Export to CSV',
                      exportOptions: {
                          modifier: {
                              search: 'applied'
                          }
                      }
                  },
                  { extend: 'colvis', className: 'btn-primary' },
              ]
          },
          initComplete: function(settings, json) {
            table.buttons().container()
            .appendTo('#datatable-buttons_wrapper .col-md-6:eq(0)');
          }
      });

Works fine, but in the event the function in the ajax handler returns NULL (no rows found). How can I tell the datatable to display something like "No data found". Right now it gives me an invalid json syntax error.

Answer 1

You can create empty json like this:

{
  "data": [],
  "total": 0,
  "recordsTotal": 0,
  "recordsFiltered": 0
}

Answer 2

Try using dataSrc and pass a function to process your data.. Hope the attached data pre-processing callback will be called even on HTTP errors

sample code

$('#example').dataTable( {
  "ajax": {
    "url": "data.json",
    "dataSrc": function ( json ) {
      for ( var i=0, ien=json.data.length ; i<ien ; i++ ) {
        json.data[i][0] = '<a href="/message/'+json.data[i][0]+'>View message</a>';
      }
      return json.data;
    }
  }
} );

Answer 3

From here Display warning if records null Datatables AJAX - dataSrc You can fix it with dataSrc

ajax: {
        url: "/assets/ajax/test_data_ajax_handler.php",
        type: "POST",
        data: {
          action: "getTestData",
          user_data: '<?=json_encode($userData)?>'
        },
        dataSrc: function(data){
            if(data.data == null){
                return [];
            } else {
                return data.data;
            }
        }
      },