text: import {Observable} from 'rxjs/Observable';
  import 'rxjs/add/observable/range';
  
  const timeStart = new Date();
  const source$ = Observable.range(1, 100000);
  
  console.log('before subscribe');
  source$.subscribe({
    complete: () => {
      console.log('Time elapsed: ' + (Date.now() - timeStart) + 'ms');
    }
  });
  console.log('after subscribe');
  
  
  
  