Observable1.ts

import { Observable } from 'rxjs';
 
const source = new Observable<number>((subscriber) => {
  subscriber.next(1);
  subscriber.next(2);
  subscriber.next(3);
  subscriber.complete();
});
 
// Usage
console.log('start');
source.subscribe({
  next: console.log,
  complete: () => console.log('done'),
});
console.log('stop');