import { Observable, of, from, interval } from 'rxjs';

// From array
const numbers$ = from([1, 2, 3, 4]);

// From promise
const user$ = from(fetch('/api/user'));

// Interval
const timer$ = interval(1000);

import { map, filter, switchMap, catchError } from 'rxjs/operators';

this.http.get<User[]>('/api/users').pipe(
  map(users => users.filter(u => u.active)),
  catchError(error => of([]))
).subscribe(users => console.log(users));

@Injectable({ providedIn: 'root' })
export class UserService {
  private users$ = new BehaviorSubject<User[]>([]);

  getUsers(): Observable<User[]> {
    return this.http.get<User[]>('/api/users').pipe(
      tap(users => this.users$.next(users)),
      catchError(this.handleError)
    );
  }

  private handleError(error: HttpErrorResponse): Observable<never> {
    console.error('Error:', error);
    return throwError(() => new Error('Something went wrong'));
  }
}