function UIEvent(ev) {
    // [Constructor(DOMString type, optional UIEventInit eventInitDict)]
    // interface UIEvent : Event {
    //     readonly    attribute Window? view;
    //     readonly    attribute long    detail;
    // };
    Event.call(this, ev);

    /**
     * @name UIEvent#detail
     * @type Number
     */
    this.detail = ev.detail;
}
See [UI Events (formerly DOM Level 3 Events)](http://www.w3.org/TR/2015/WD-uievents-20150428).

@class UIEvent
@augments Event

@param  {Event} ev   The native DOM event.