What happens when filter is passed in pipe?

I am trying to understand why the below subscription is not working:

  isLoggedIn1$:Observable<boolean> = of(false) // on subscribing it I get value as false

  isLoggedIn2$:Observable<boolean> = of(false).pipe(filter(value => Boolean(value))) // this one is not giving any value even it looks like subscribe is not getting called for this

Is there any documentation for this particular behavior?

As I understand it is being treated equivalent to EMPTY. but then why I am not getting type error for second one.

Solution 1:

The filter operator filters the value based on given predicate. If that condition specified by filter is fulfilled, then the value will pass down to subscriber else we don't see anything on screen.

For the line

isLoggedIn2$:Observable<boolean> = of(false).pipe(filter(value => Boolean(value)))

The predicate here only allows those value to pass further down the pipe that are true

value => Boolean(value) 

If you want to print false you have to modify filter condition as

value => Boolean(value) === false

More on filter operator - https://www.learnrxjs.io/learn-rxjs/operators/filtering/filter