Angular Web Framework RxJS & Observables 3

Question 1

What does `forkJoin` emit when all source Observables complete?

Accepted Answer

An array of the last values from each source Observable

Answer

forkJoin waits for all source Observables to complete, then emits a single array containing each source's final emitted value.

Question 2

Which RxJS operator delays each emission by a specified time but does not drop values?

Accepted Answer

delay

Answer

delay shifts every emission forward in time by the specified duration without discarding any values.

Question 3

What is the role of `pipe()` in RxJS?

Accepted Answer

Chains multiple operators together into a single transformation

Answer

pipe() composes multiple RxJS operators in sequence, passing each operator's output as input to the next.

Question 4

Which operator would you use to handle errors by retrying the source Observable a fixed number of times?

Accepted Answer

retry

Answer

retry(n) resubscribes to the source Observable up to n times when it errors before propagating the error.

Question 5

What does `exhaustMap` do that differs from `mergeMap` and `switchMap`?

Accepted Answer

It ignores new source values while the current inner Observable is still active

Answer

exhaustMap drops incoming source values entirely while an inner Observable is in progress, preventing overlapping requests.

Angular Web Framework Practice Test