title: Resetting ReplaySubject in RxJS 6
body: <p>I have a filterable 'activity log' that's currently implemented using a <code>ReplaySubject</code> (since a few components use it and they might subscribe at different times).</p>
  
  <p>When the user changes the filter settings, a new request is made, however the results are appended to the <code>ReplaySubject</code> rather than replacing it.</p>
  
  <p>I was wondering if there is anyway to update the <code>ReplaySubject</code> to only send through the new items using something like a <code>switchMap</code>?</p>
  
  <p>Otherwise, I might need to either use a <code>BehaviorSubject</code> that returns an array of all the activity entries or recreate the <code>ReplaySubject</code> and notify users (probably by using another observable) to unsubscribe and resubscribe to the new observable.</p>