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

repeatwhen is an operator used to re-subscribe to the source Observable when a second Observable (the notifier) emits a value. Here's an example of how to use repeatwhen:

index.tsx
import { interval } from 'rxjs';
import { repeatwhen, take } from 'rxjs/operators';

const source$ = interval(1000)
  .pipe(
    take(5),
    repeatwhen(notifier => notifier)
  )
  .subscribe({
    next: value => console.log(value),
    error: err => console.log('Error:', err),
    complete: () => console.log('Complete')
  });
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In this example, the source Observable emits a value every second (using the interval function), but we only want to take the first 5 values (using the take operator). After that, the repeatwhen operator resubscribes to the source Observable whenever notifier emits a value (in this case, we're just passing through notifier directly).

It's worth noting that repeatwhen receives the notifier Observable as a parameter and expects it to emit a value. If notifier completes or errors out, the entire subscription completes or errors out and repeatwhen has no effect.

Also, repeatwhen does not work with Observables that complete synchronously (such as using of to create an Observable with a finite amount of values) because it will resubscribe before the initial subscription has completed. In those scenarios, use repeat instead.