TypeError: Cannot read property 'split' of undefined (crashes site on logout)

Hi guys, this issue only occurs when the user is logged out and completely crashes the app. I get a bunch of errors about not being able to read ‘split’ of undefined.

AppComponent_Host.ngfactory.js? [sm]:1 ERROR TypeError: Cannot read property 'split' of undefined
    at JwtHelperService.push../node_modules/@auth0/angular-jwt/src/jwthelper.service.js.JwtHelperService.decodeToken (jwthelper.service.js:70)
    at JwtHelperService.push../node_modules/@auth0/angular-jwt/src/jwthelper.service.js.JwtHelperService.getTokenExpirationDate (jwthelper.service.js:83)
    at JwtHelperService.push../node_modules/@auth0/angular-jwt/src/jwthelper.service.js.JwtHelperService.isTokenExpired (jwthelper.service.js:96)
    at AuthService.push../src/app/core/auth/auth.service.ts.AuthService.isLoggedIn (auth.service.ts:124)

As I said, this only happens when the user logs out but completely crashed the app so they can’t log back in.

Here’s how JWT is implemented, it’s been this way for a few months and nothing’s changed so I have no idea what is going on here.

app.module.ts

export function tokenGetter() {
  const user = JSON.parse(localStorage.getItem('user'));
  const userToken = user ? user.token : null;
  return userToken;
}

...

JwtModule.forRoot({
  config: {
    tokenGetter: tokenGetter,
    whitelistedDomains: ['localhost:4200']
  }
}),

auth.service.ts

import { JwtHelperService } from '@auth0/angular-jwt';

constructor(
    private http: HttpClient,
    private jwtHelper: JwtHelperService
  ) {}

...

isLoggedIn() {
  return this.jwtHelper.isTokenExpired() ? false : true;
}

The only way I can get back into the app to log back in is to comment out the return statement within the isLoggedIn function.

Any help would be very much appreciated, thanks.

[gethinoakes]

Thanks @d-go, that is much cleaner. I look forward to when isTokenExpired returns false for null tokens 🙂

[d-go]

Well… it seems that actually the isTokenExpired() method doesn’t handle null tokens, however, I think you can simplify your solution:

isLoggedIn() {
    const token = this.jwtHelper.tokenGetter();
    if (!token) return false;

    return !this.jwtHelper.isTokenExpired();
}

But I agree that if the token is null, the method should treat the token as expired