let textField = $('#searchUser');
        textField.on('keyup', function () {

            const textFieldValue = $(textField).val();

            if (textFieldValue.length > 3) {

                $.ajax({
                    headers: {
                        'X-CSRF-TOKEN': $('meta[name="csrf-token"]').attr('content')
                    },
                    dataType: 'json',
                    type: "POST",
                    url: '/search',
                    data: {
                        'string': textFieldValue
                    },
                    success: function (response) {

                        console.log(response);
                        console.log(textFieldValue);
                    }


                });
            }

        });


    /**
     * @param Request $request
     * @return JsonResponse
     */
    public function searchUser(Request $request): JsonResponse
    {
        $string = $request->input('searchUser');

        $user = DB::table('users')->where('name', 'LIKE','%'. $string.'%')
            ->orWhere('surname', 'LIKE','%'. $string.'%')
            ->orWhere('phone_number', 'LIKE','%'. $string.'%')
            ->orWhere('email', 'LIKE','%'. $string.'%')


            ->get();


        return response()->json([
            'user' => $user,
            'string' => $string,
            'request'=>$request
        ]);
    }

            <form method="POST" action="{{ route('admin.search-user') }}">
                @csrf

                <div class="form-group row" id="searchUserForm">
                    <label for="searchUser"
                           class="col-md-4 col-form-label text-md-right">{{ __('Wyszukaj użytkownika') }}</label>

                    <div class="col-md-6">

                        <input class="form-control" id="searchUser"
                               placeholder="Wyszukaj użytkownika..." name="searchUser">
                    </div>

                </div>
            </form>