Angular Firebase Router Guard with Browser Refresh

auth.guard.ts

import { Injectable } from '@angular/core';
import { CanActivate, ActivatedRouteSnapshot, RouterStateSnapshot, Router } from '@angular/router';
import { Observable } from 'rxjs/Observable';
import { AngularFireAuth } from 'angularfire2/auth';
import 'rxjs/add/operator/do';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/take';

@Injectable()
export class AuthGuard implements CanActivate {
  constructor(private afAuth: AngularFireAuth, private router: Router) {}


  canActivate(
    next: ActivatedRouteSnapshot,
    state: RouterStateSnapshot): Observable<boolean> {

      return this.afAuth.authState
       .take(1)
       .map(user => !!user)
       .do(loggedIn => {
         if (!loggedIn) {
           console.log("access denied")
           this.router.navigate(['/login']);
         }
     })
   }

}