#import // https://html.spec.whatwg.org/multipage/nav-history-apis.html#popstateevent [Exposed=Window] interface PopStateEvent : Event { constructor(DOMString type, optional PopStateEventInit eventInitDict = {}); readonly attribute any state; [FIXME] readonly attribute boolean hasUAVisualTransition; }; dictionary PopStateEventInit : EventInit { any state = null; // FIXME: boolean hasUAVisualTransition = false; };