last-value-from-default.ts

import { EmptyError, lastValueFrom, Observable, Subject } from 'rxjs';

async function demo<T>(observable: Observable<T>): Promise<void> {
  try {
    const promiseResult = await lastValueFrom(observable, { defaultValue: 25 });

    console.log(promiseResult);
  } catch (error) {
    console.log(error instanceof EmptyError);
    console.error(error);
  }
}

const subject = new Subject();
demo(subject.asObservable());
subject.complete();