-import { Route, PreloadingStrategy } from '@angular/router'
-import { Observable } from 'rxjs/Observable'
-import 'rxjs/add/observable/timer'
-import 'rxjs/add/operator/switchMap'
+import { Observable, timer as observableTimer, of as ofObservable } from 'rxjs'
+import { switchMap } from 'rxjs/operators'
+import { PreloadingStrategy, Route } from '@angular/router'