The PubSub library includes a number of topics out of the box and these topics are described in PubSub topics. If you need to create a custom topic, you can do so using the topic() function, passing in the ID of your topic. The topic() function returns an existing topic if the ID already exists. If no topics exist that match the passed ID, a new topic is created and returned.

Custom topic objects have the publish, publishWith, subscribe, and unsubscribe functions. Note that custom topics are available for subscription by custom widgets only; out-of-the-box widgets will have no knowledge of or access to custom topics. They are used exclusively to let one custom widget know about an event that has happened in another custom widget. Oracle recommends that any custom topics you create include a merchant-specific prefix in the topic ID to avoid conflicts with out-of-the-box topics.

The following example shows the creation of a topic named MY_TOPIC in a custom widget:

$.Topic("MY_TOPIC.memory").publish("Message is here") ;

This example shows a subscription to MY_TOPIC in another custom widget:

$.Topic("MY_TOPIC.memory ").subscribe(function(message)
{
    console.log("Message is: " + message);
});

Note that this custom topic makes use of the .memory suffix, which enables memory for the topic. Typically, for a callback function to be triggered, it has to be subscribed to a topic before any messages are published to that topic. The .memory suffix allows a callback function to be triggered for the most recently published message even if the function has subscribed to the topic after the message was published.