To handle possible access or authentication exceptions that may occur while the application is running (after the user has successfully logged in), you can provide a handler for the accessViolation platform event.

platform.on(platform.events.accessViolation, function(e){

    // do something

});

A recommended way to handle access or authentication exceptions is to direct the user to the login page or UI. The login page may attempt to automatically re-authenticate the user using stored authentication data (see below).