Jquery - autocomplete - Returns specific code if the search failed

I need some help on an autocomplete, when I do a search everything works fine if the item is in the list, I get the ID and return it in the dedicated input.

But is there a way to return a code 9998 if the search fails?

The jquery part :

$input_idenseigne=$('div.id_enseigne span.cell-sub-wrapper span.cell-input input');
$input_enseigne=   $('div.enseigne span.cell-sub-wrapper span.cell-input input');     

      
    
       var getItems = function(term, callback) {
            loading = true;
            $.ajax( {
                type: 'GET',
                url: "XXX",
                dataType: "json",
                data: {
                term: term
                },
                success: function( data ) {
                    loading = true;
                    callback($.map(data, function ( item ) {
                        return {
                            value: item[0],
                            label: item[1]
                        }
                    }));
                    
                   
                },
          error: function ( data ) {
            alert('error');
          }
                
                    
            });
        };
    
        var fillFields = function(item) {
        };
    
    


      $('input.ui-autocomplete-input').each(function() {
                  
    $(this).blur(function(){
     var keyEvent = $.Event("keydown");
     keyEvent.keyCode = $.ui.keyCode.ENTER;
     $(this).trigger(keyEvent);
     
            
     if ($(this).val().length >= 3) {
       getItems($(this).val(), function(items) {
        if (items.length) {    }
               
       });
     }
    }).autocomplete({
 
    source: function(request, response) {
         getItems(request.term, response);
    },
    minLength: 3,
    search: function( event, ui ) { },
    select: function( event, ui)     {
        event.preventDefault();
        $ ('div.id_enseigne span.cell-sub-wrapper span.cell-input input').val(ui.item.value);
        $ ('input.ui-autocomplete-input').val(ui.item.label);
        
            }
  });
  });

And the html part :

<div class="answers answers-list">

  <div class="element even  groupingCols OneColumnEl hasError   id_enseigne ">
<span class="cell-sub-wrapper cell-legend-above">
<span class="cell-text cell-sub-column"></span>
<span class="cell-input cell-sub-column">
  <input type="text" name="ans3414" id="ans3414" value="" size="25">
</span>
</span>
</div>
<div class="element even  groupingCols OneColumnEl hasError enseigne ">
<span class="cell-sub-wrapper cell-legend-above">
<span class="cell-text cell-sub-column"></span>
<span class="cell-input cell-sub-column">
  <input type="text" name="ans3415" id="ans3415" value="" size="25" class="ui-autocomplete-input" autocomplete="off"/>
</span>
</span>
</div>

  </div>

Thanks you

I tried different methods with the following code for example, but it does not work:

,
          error: function ( data ) {
            alert('error');
          }