Ending Subscriptions

With asynchronous message processing, when a subscription is successfully made, messages will begin flowing to the message handler function and the Client.subscribe() call returns a Promise object that resolves with a unique string that serves as the identifier for this subscription. A Client can have any number of active subscriptions, and this string is used to refer to the particular subscription we have made here. For example, to unsubscribe, we simply pass in this identifier:

const client = new Client('exampleClient');
await client.connect('wss://localhost:9000/amps/json');

const subId = await client.subscribe(onMessagePrinter, 'messages');

// when the program is done with the subscription, unsubscribe
await client.unsubscribe(subId);
console.log('Unsubscribed');

In this example, as in the previous section, we use the Client.subscribe() method to create a subscription to the messages topic. When our application is done listening to this topic, it unsubscribes by passing in the subId passed from the successfully resolved Promise of subscribe(). After the subscription is removed, no more messages will flow into our onMessagePrinter function.

AMPS also accepts the keyword all to unsubscribe all subscriptions for the client.