get data based on select dropdown list

i have this two tables

customer customer table

           protected $fillable= 
               ['compy_name','phone','address_name','master_price','customer_type','slave_price','currency'];

customer order table.

           protected $fillable=[  
                                   'orderNumb',
                                  'customer_id',
                                  'loading_point',
                                   'looade_date',
                                    'border_id',
                                    'team_id',
                                    'truck_number',
                                     'trailer_number',
                                        'master_qty',
                                      'slave_qty',
                                       'user_id'  ];

so i want when i select the compy_name, i get their truck_number as well.

i tried like this but does not works

                  Route::get('customers/{customer}/customer__orders', function (App\Customer_Orders $customer) 
              {
               return response()->json($customer->customer_order->map(function ($customer_order) {
                 return ['id' => $customer_order->id, 'text' => $customer_order->truck_number];
           })
        );
     });

in my blade

             $(document).ready(function(){
      $("#customer_id").change(function () {
          var options = [];
          $.ajax({
            method: 'GET',
            url: '/customers/' + this.value + '/customer__orders',
            success: function (options) {
                window.options = options
                $('#truck_id').empty()
                $('#truck_id').select2({data: options});
            }
          })
      })
      })

correct me where i did wrong