What's the point of AsyncSubject in RXJS?

Question

The documentation for RxJS defines AsyncSubject as follows:

The AsyncSubject is a variant where only the last value of the O

Answer 1

Cool!

And just for fun, I added handlers to log complete events to show they are raised in either case (Subject or AsyncSubject) when a subscribe happens after a subject is completed.

Also added BehaviorSubject.

const subject = new Rx.Subject();
const asyncSubject = new Rx.AsyncSubject();
const behaviorSubject = new Rx.BehaviorSubject();

console.log('before init - behaviorSubject', behaviorSubject.value)

subject.next('INIT');
asyncSubject.next('INIT');
behaviorSubject.next('INIT');

console.log('before subscribe - behaviorSubject', behaviorSubject.value)

// Subscribe before
subject.subscribe(x => console.log('before complete - subject', x))
asyncSubject.subscribe(x => console.log('before complete - asyncSubject', x))
behaviorSubject.subscribe(x => console.log('before complete - behaviorSubject', x))

subject.next('NEXT');
subject.complete();

asyncSubject.next('NEXT');
asyncSubject.complete();

behaviorSubject.next('NEXT');
behaviorSubject.complete();

// Subscribe after
subject.subscribe({
  next: x => console.log('after complete - subject', x),
  complete: () => console.log('after complete - subject COMPLETE')
})
asyncSubject.subscribe({
  next: x => console.log('after complete - asyncSubject', x),
  complete: () => console.log('after complete - asyncSubject COMPLETE')
})
behaviorSubject.subscribe({
  next: x => console.log('after complete - behaviorSubject', x),
  complete: () => console.log('after complete - behaviorSubject COMPLETE')
})

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