throwIfEmpty

If the source observable completes without emitting a value, it will emit an error. The error will be created at that time by the optional errorFactory argument, otherwise, the error will be EmptyError.

Example

Throw an error if the document wasn't clicked within 1 second

import { fromEvent, takeUntil, timer, throwIfEmpty } from 'rxjs';

const click$ = fromEvent(document, 'click');

click$.pipe(
  takeUntil(timer(1000)),
  throwIfEmpty(() => new Error('The document was not clicked within 1 second'))
)
.subscribe({
  next() {
   console.log('The document was clicked');
  },
  error(err) {
    console.error(err.message);
  }
});