问Laravel ajax表单数据未发布到控制器

EN

<form class="buy-product-form" id="{{$product->id}}" action="{{url('/UoE/buy-product')}}" method="POST">
                                    {{csrf_field()}}
                                    <button class="pull-right btn btn-primary">BUY NOW</button>
                                </form>

$(document).ready(function(){
            $.ajaxSetup({
                headers: {
                    'X-CSRF-TOKEN': $('meta[name="csrf-token"]').attr('content')
                }
            });
            $('form.buy-product-form').on('submit', (function (e) {
                e.preventDefault();
                var product_id = $(this).closest("form").attr("id");
                $.ajax({
                    url: $(this).closest("form").attr('action'),
                    type: 'POST',
                    data: {'id': product_id},
                    dataType: 'JSON',
                    success: function () {
                        window.alert($(this).closest("form").attr('action'));
                    }
                });
            }));
        });

 public function buyProduct(Request $request){
        $product_id = $request->id;

Route::post('/{university_code}/buy-product', 'UserController@buyProduct');