How to fix "Type Error: b.toLowerCase is not a function" typeahead.js?

I'm working on autocomplete search with typeahead plugin. I used Laravel 5.5, query builder, ajax and jquery. When I type in the surname box nothing happens on screen and the console returns this error:

TypeError: b.toLowerCase is not a function. 
    matcher http://127.0.0.1:8000/js/typeahead.js:1
    b http://127.0.0.1:8000/js/typeahead.js:1
    grep jQuery
    process http://127.0.0.1:8000/js/typeahead.js:1
    i jQuery
    success http://127.0.0.1:8000/referti:257

    jQuery 4
        c
        fireWith
        l
        o

This is the implemented code:

1. Header:

   <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
   
   <link rel="stylesheet" type="text/css" href="">
   <link rel="stylesheet" type="text/css" href="">
   
   <script src="https://code.jquery.com/jquery-3.4.1.min.js" integrity="sha256-CSXorXvZcTkaix6Yvo6HppcZGetbYMGWSFlBw8HfCJo=" crossorigin="anonymous"></script>
   <script src="" ></script>
   

2. Form:

   <div class="form-container">
                   <div class="form-group">
                       <label for="cognome">Cognome:</label>
                       <input class="typeahead form-control" type="text" id="cognome" autocomplete="off" placeholder="Cognome"/>
                   </div>
   

3. Script:

   $(document).ready(function () { 
   
     _token = $('meta[name="csrf-token"]').attr('content');
     $('#cognome').typeahead({
       source: function (query, result) {
           console.log('-->', query);
           $.ajax({
               url: "/referti/searchBySurname",
               method: "post",
               data: {query: query, _token: _token },            
               dataType: "json",
               success: function (data) {
                   //console.log(data);
                   result($.map(data, function (item) {
                       return item;
                   })); 
                }
             });
           }
       });
   });
   

4. Controller:

   class RefertiController extends Controller{
   
      public function searchBySurname(Request $request){ 
      $data = $request->get('query');
   
      Log::info('-->' . $data); 
      $reports = DB::table('PATIENT')
          ->where('LAST_NAME', 'LIKE', "%$data%")
          ->get();
      Log::info($reports);
      return json_encode($reports);
      }
   }
   

5. This is a part of what the . log file produces, correctly:

   [2019-09-26 13:54:57] local.INFO:                                                                  
   
   [{"PATIENT_KEY":"19234283CDGIULIANI ","LAST_NAME":"GIULIANI","FIRST_NAME":"ADELE","BIRTHDATE":"1923-04-28","SEX":"F","ETHNICITY":null,"REF_PHYSICIAN":null,"PAT_COMMENT":"ister-ann bil","MENOPAUSE_YEAR":-1},
   
   {"PATIENT_KEY":"19261214BEGIULIANAT","LAST_NAME":"GIULIANATI","FIRST_NAME":"SENICE","BIRTHDATE":"1926-01-20","SEX":"F","ETHNICITY":"W","REF_PHYSICIAN":null,"PAT_COMMENT":"postmenopausa spontanea","MENOPAUSE_YEAR":-1},...
   

What can I do to solve the problem? Where am I wrong? Thanks to whoever answers!

via Chebli Mohamed