How can I subscribe to topic?

[FamilyMan]

Apparently firebase can use something like:

FirebaseMessaging.getInstance().subscribeToTopic("all")
            .addOnCompleteListener { task ->
                if (task.isSuccessful) {
                    //Successfully Subscribed to Notification Service
                }else{
                //Subscription  Notification Service failed
                }
            }

How can I subscribe to a topic using this module?

[FamilyMan]

There is no client-side API in the JavaScript SDK to subscribe to a topic. You'll instead need to use a (server-side) Admin SDK to accomplish this.

For example, the subscribeToTopic method you refer to exists in the Node.js SDK and in the Java SDK, but not in the JavaScript/Web or Android SDKs.

I recommend studying the documentation on subscribing a web client to a topic a bit further: https://firebase.google.com/docs/cloud-messaging/js/topic-messaging#subscribe_the_client_app_to_a_topic

[JTibblesSoftcon]

Thanks for this information. I've been scratching my head for days on this.
Also, do we know why susbscribeToTopics isn't available on the client-side API? It makes sense to have included it as they do with their other available apis like getToken