Nobody has to use HostListener
In Angular event handling is often implemented using the hostListener decorator, even though it might not be the best fit for the problem.
takeWhile, takeUntil, takeWhat?
The RxJS TakeWhile and TakeUntil operator already sound similar and behave similarly. So what's the difference?
About switchMap and friends
This blog article covers the details about the RxJS switchMap operator, but also mergeMap, concatMap and exhaustMap.