Presence

Presence is a powerful feature that allows clients to be aware of other participants currently active on a channel. Each participant in a channel is uniquely identified by:

1. A self-assigned client identifier
2. A system-assigned connection identifier
3. An optional payload for additional status or attribute information

This feature is particularly useful for rapidly developing real-time applications such as:

• Chat rooms
• Multiplayer games
• Collaborative tools

Presence automatically tracks and updates the status of all participants across various devices in real-time, simplifying the development of interactive, multi-user applications.

Accessing Presence

The presence feature is accessed through the participant property of a channel. Once you have connected to a channel, you can interact with the presence functionality as follows:

const channel = await realtime.connect('channel-name');
const presence = channel.participant;

Updating Presence

To update your presence information, use the update() method. This allows you to set or modify any custom data associated with your presence:

channel.participant.update({ name: "John", status: "online" });

Subscribing to Presence Events

You can subscribe to presence events to receive updates about participants joining, leaving, or updating their status. Use the subscribe() method with the appropriate event type:

const callback = ({ data }) => {
  console.log("Presence update", data);
};

channel.participant.subscribe("presence.update", callback);

Available presence events are:

• presence.joined-room: Triggered when a participant joins the channel
• presence.leave: Triggered when a participant leaves the channel
• presence.update: Triggered when a participant updates their presence data

Unsubscribing from Presence Events

To stop receiving updates for a specific presence event, use the unsubscribe() method:

channel.participant.unsubscribe("presence.update");

Getting All Presence Information

To retrieve the current presence information for all participants in the channel, use the getAll() method:

const presences = channel.participant.getAll();
console.log(presences);

This method returns an array containing presence information for all participants in the channel. Here's an example of what the returned data might look like:

[
    {
        "connectionId": "80NFb-QRx3UljIIdADWo",
        "data": {
            "mostHatedCandy": "Bit-O-Honey",
            "favoriteCandy": "Chocolate"
        },
        "id": "luke-long",
        "name": "Luke Long",
        "timestamp": 1728668099104
    }
]

In this example:

• connectionId is the unique identifier for this participant's connection
• data contains custom information set by the participant
• id is the participant's unique identifier
• name is the participant's name
• timestamp is the Unix timestamp of when this presence information was last updated

You can use this data to display information about current participants in your application, such as a list of active users or their current status.