adding change listener to dropwdown in custom editor window

 <input type = "text"   id="classOptions" class="e-field" name="classOptions"/>

onPopupOpen(args: PopupOpenEventArgs): void {

  if (args.type === 'Editor') {

 let classOptElement: HTMLInputElement = args.element.querySelector('#classOptions');

      let classOptObject : DropDownList = new DropDownList ({ fields: { text: 'option', value: 'id' },

      dataSource: <any>this.classOptions});

      classOptObject.appendTo(classOptElement)

}}

In the above example, I am adding a dropdownlist component to my custom editor window. How can I add a change listener to it? Usually, we could use the onChange event, but I am not sure how I could use it INSIDE the onPopupOpen event. Can you provide a working example?