Property 'of' does not exist on type 'typeof Observable [duplicate]
You need to import it:
for Angular >= 6.0.0
uses RxJS 6.0.0 Angular Changelog 6.0.0
import { of } from 'rxjs';
And its usage has been changed, you no longer call it off of Observable:
of('token');
RxJS v5.x to v6 Update Guide - HowTo: Convert to pipe syntax which uses of()
for Angular <= 5.x.xx
import 'rxjs/add/observable/of';
And it's used as you have in your question
Observable.of('token');