how to use the subscribeon function from the rxjs library in javascript

The subscribeOn operator in RxJS library allows us to specify on which scheduler we want to subscribe to a Observable. This can be useful when we want to delay the subscription to an Observable until a certain time, or when we want to make sure that the subscription is done on a specific thread or context.

Here's an example of how to use subscribeOn to subscribe to an Observable on a separate scheduler:

index.tsx
import { fromEvent, asyncScheduler } from 'rxjs';
import { subscribeOn } from 'rxjs/operators';

const button = document.getElementById('myButton');
const click$ = fromEvent(button, 'click');

console.log('Before subscription');

click$.pipe(
  subscribeOn(asyncScheduler)
).subscribe(
  event => console.log('Clicked!', event),
  error => console.error('Error!', error),
  () => console.log('Completed!')
);

console.log('After subscription');
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In this example, we are using the asyncScheduler to subscribe to the click$ Observable, which means that the click$ events will be processed on a separate thread from the main UI thread. This is useful when we don't want the event processing to block the UI.

Note that subscribeOn only affects the subscription of the Observable, and not the emission of the events. If you want to control the emission of events, you can use the observeOn operator instead.