Mastering TypeScript 3 - Third Edition

Using Observables in anger – of, pipe, and map

We now have a REST endpoint that can verify our JWT token. What we need to do, then, is to call this endpoint from our Angular application to ensure that the user that is logged in has a valid JWT token. Remember that when we log in, we store this token in Local Storage, and redirect to our SecureComponent. The SecureComponent is protected by our AuthGuard, which checks for the existence of this token. We therefore need to contact our Express server, which generated this token, in order to verify it.

The most obvious place to put this code is in the AuthGuard itself, so that any attempt to access the SecureComponent will need to verify the JWT token by POSTing to our Express server before continuing. ...