求个Dcatadmin的js监听表单demo

有个需求需要动态获取下拉菜单的值传到接口以获取联动数据，js监听实在没搞懂，求给个例子或帮下忙，以下是源代码,只需要动态获取model_type下拉选中的值

return Form::make(new Card(), function (Form $form) {


            $form->display('id');
            $form->text('card_id');
            if (isset(request()->school_id)) {
                $form->select('model_type', '卡片类型')->options([User::class => '教师卡', Student::class => '学生卡'])->load('school_class', 'school_class?school_id=' . request()->school_id);
                $form->select('school_class', '筛选班级')->load('model_id', 'model_id?model_type=' . base64_encode(<<<JS
Dcat.init('.selector[name=model_type]',function ($this, id) {

})
JS
                    ));
                $form->ignore(['school_class']);
                $form->select('model_id');
                $form->hidden('card_type')->default(0);
                $form->hidden('school_id')->value(request()->school_id);
                $form->select('school_class_id')->options(function () {
                    return SchoolClass::where('school_id', request()->school_id)->pluck('class_name', 'id');
                });
            }
            $form->display('created_at');
            $form->display('updated_at');
        });