function
stable
Asynchronously subscribes Observers to this Observable on the specified SchedulerLike
.
subscribeOn<T>(scheduler: SchedulerLike, delay: number = 0): MonoTypeOperatorFunction<T>
scheduler | The |
delay | Optional. Default is Type: |
MonoTypeOperatorFunction<T>
: The source Observable modified so that its subscriptions happen on the specified SchedulerLike
. .
With subscribeOn
you can decide what type of scheduler a specific Observable will be using when it is subscribed to.
Schedulers control the speed and order of emissions to observers from an Observable stream.
Given the following code:
import { of, merge } from 'rxjs'; const a = of(1, 2, 3, 4); const b = of(5, 6, 7, 8, 9); merge(a, b).subscribe(console.log);
Both Observable a
and b
will emit their values directly and synchronously once they are subscribed to. This will result in the output of 1 2 3 4 5 6 7 8 9
.
But if we instead us the subscribeOn
operator declaring that we want to use the async
for values emited by Observable a
:
import { of, merge, asyncScheduler } from 'rxjs'; import { subscribeOn } from 'rxjs/operators'; const a = of(1, 2, 3, 4).pipe(subscribeOn(asyncScheduler)); const b = of(5, 6, 7, 8, 9); merge(a, b).subscribe(console.log);
The output will instead be 5 6 7 8 9 1 2 3 4
. The reason for this is that Observable b
emits its values directly and synchronously like before but the emissions from a
are scheduled on the event loop because we are now using the async
for that specific Observable.
© 2015–2018 Google, Inc., Netflix, Inc., Microsoft Corp. and contributors.
Code licensed under an Apache-2.0 License. Documentation licensed under CC BY 4.0.
https://rxjs.dev/api/operators/subscribeOn