I want to get the authentication into an Angular application with Okta, I followed the instuctions step by step in the documentation : <https://developer.okta.com/code/angular/okta_angular_sign-in_widget/>
But I get an error when I try to start the server, Can you help me please ? 

```
export class AppComponent {
 title = 'okta';
  isAuthenticated: boolean;

    constructor(public oktaAuth: OktaAuthService, public router: Router) {
        // Subscribe to authentication state changes
        this.oktaAuth.$authenticationState.subscribe(
            (isAuthenticated: boolean)  => this.isAuthenticated = isAuthenticated
        );
    }

    async ngOnInit() {
        // Get the authentication state for immediate use
        this.isAuthenticated = await this.oktaAuth.isAuthenticated();
    }

```

! console error

[console error](https://i.stack.imgur.com/zVJoG.png)