RXJS, finalize is same as finally can only be used whe observable complete or subject completes

 Observable automatically completes after emission for example of(1), observer=> observer.next(1) hence for observable, usally piple(fianlize()) can always be used. Note finalize is always called in the end when observable completes.

For subject, it does not complete after next, subject.next(1), subject.next(2), it can keep emitting, for subject to complete use

var complete  = subject.piple(take(1))

https://stackoverflow.com/questions/49735826/rxjs5-finalize-operator-not-called

For some observable, it may not always be completed after emission such as this.route.queryParams,

Need to call  this.route.queryParams.pipe(take(1)),

https://stackoverflow.com/questions/49735826/rxjs5-finalize-operator-not-called