title: Proper way of creating an observable with a meaningful pipe but meaningless content
body: <p>I'm creating an algorithm for displaying an alert/modal that prompts users to take action or be logged out of the application when he/she has been unactive for x amount of seconds, where x is lower than the timeout y on the refresh token.</p>
  
  <p>How long the duration is calculated to be is irrelevant, but I'm solving the issue with RxJs.</p>
  
  <p>I've reached the following pipe that seems to do the work:</p>
  
  <pre><code>this.countDown$
   .pipe(
     distinctUntilChanged(),
     switchMap(exp =&gt;
       of(null).pipe(
         delay(AuthService.CalculateDelayTime(exp))
       )
     )
   )
   .subscribe(AuthService.TriggerModal);
  
  </code></pre>
  
  <p><code>countDown$</code> is a <code>Subject&lt;number&gt;</code> that is continuously fed expiry time of the refresh token whenever route authentication is performed.</p>
  
  <p><code>CalculateDelayTime</code> and <code>TriggerModal</code> are both static methods (for now, as the modal itself has not been implemented; calculate returns an amount of seconds until the modal should appear).</p>
  
  <p>Overall it seems to be what I want, but I'm a bit concerned of the <code>of(null)</code>. Is there a more correct/RxJs-style/elegant way to solve this specific problem? I do need the exp time for the delay-function, and I also want to reset the delay with each unique expirytime that comes in (which is why I use <code>switchMap</code>). 
  However doing <code>of(exp)</code> suggests I am actually manipulating <code>exp</code> as a part of the inner pipe, which I am not.</p>
  
  <p>I tried <code>Observable.empty()</code> but it seemed like the inner observable would not trigger.</p>
  
  <p>Any suggestions how this should be done?</p>