ng-reactive-sticky-header#share-stream.ts

const scroll$ = fromEvent(window, 'scroll').pipe(
  throttleTime(10),
  map(() => window.pageYOffset),
  pairwise(),
  map(([y1, y2]): Direction => (y2 < y1 ? Direction.Up : Direction.Down)),
  distinctUntilChanged(),
  share()
);

const scrollUp$ = scroll$.pipe(
  filter(direction => direction === Direction.Up)
);

const scrollDown$ = scroll$.pipe(
  filter(direction => direction === Direction.Down)
);