Konami RXJS 6

konami.ts

let keyDowns$: Observable<Event | string> = fromEvent(document, 'keyup');
keyDowns$ = keyDowns$.pipe(
  map((event: KeyboardEvent) => event.code),
  bufferCount(10, 1),
  map(codes => codes.join(',')),
  filter(codes => codes === "ArrowUp,ArrowUp,ArrowDown,ArrowDown,ArrowLeft,ArrowRight,ArrowLeft,ArrowRight,KeyB,KeyQ")
)

keyDowns$.subscribe(() => {
  this.setState({admin: !this.state.admin, item: null});
});