Check user presence

PubNub allows you to track the online and offline status of users and devices in real time. This means that you can look up, among other things, who's currently online, when a user has joined/left a channel or which channels a user is subscribed to.

The code below will print to the console a list of all users who are online on the chats.public.release_announcements channel.

pubnub.hereNow(
{
channels: ["chats.public.release_announcements"]
},
function (status, response) {
console.log(status, response);
}
);

Checking presence is based on receiving presence events which are sent automatically from the PubNub servers when a user's state changes. You can react to these events by handling them using a handler dedicated to presence events.

Presence events aren't sent on the channel where a change in presence happens. They're sent on a presence channel, which is a helper channel that gets created automatically for every regular channel. As it behaves like a normal channel, to receive the data sent to it, you must subscribe to the presence channel.

If you know you will be interested in real-time presence changes, it's best to do it when you subscribe to the regular channel.

// subscribe to a single channel without presence
pubnub.subscribe({channels: ["chats_inbox.user_1905"]});

// subscribe to multiple channels with presence
pubnub.subscribe({
channels: [
"chats_guilds.mages_guild",
"alerts.system",
"geolocation.data"
],
withPresence: true
});

As a part of user presence, you can set a custom dynamic state, like current score or mood indicator, for the users in your channels. However, this state persists only as long as the user is subscribed to a channel. Once the user disconnects, that custom data is lost.

If you don't want to lose any additional data about your users and channels, consider adding metadata.

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