Nirvana JavaScript : Using a NirvanaChannel

The Nirvana Channel object (NirvanaChannel) is a simple JavaScript wrapper for a native Nirvana Channel.

Note that unlike the Enterprise APIs, the JavaScript API does not support programmatic creation of channels; instead, you can use the Enterprise Manager GUI to create a Nirvana Channel.

This JavaScript code snippet demonstrates how to create a JavaScript NirvanaChannel object, which allows you to publish or subscribe to such a channel: 

var demoChannel = new NirvanaChannel("/some/demo/channel");

NirvanaChannel offers three important functions:

  • demoChannel.subscribe()
  • demoChannel.unsubscribe()
  • demoChannel.publish(Nirvana.nConsumeEvent event)

Each of these functions will invoke a minimal callback function which is implemented in the NirvanaChannel object, but which you can (and probably should) override with your own business-specific implementations.

The callback functions are:

  • NirvanaChannel.onData(nEvent)

    invoked when an event is received from a channel

  • NirvanaChannel.onSubscribe(channelName, msg)

    invoked after successfully subscribing (an empty implementation can be fine)

  • NirvanaChannel.onUnsubscribe(channelName)

    invoked after successfully unsubscribing (an empty implementation can be fine)

  • NirvanaChannel.onPublish(status)

    invoked after an event is successfully published (an empty implementation can be fine)

  • NirvanaChannel.onError(errorMessage)

    invoked after any unexpected error

As mentioned above, each of these callback functions can be overriden in your code either with an anonymous function: 

 	demoChannel.onData = function(event) {
 		// do something with the event
 	}

or, if you prefer, with a named function within your code: 

 	function myEventHandler(event) {
 		// do something with the event
 	}
 	demoChannel.onData = myEventHandler;
See Subscribing to a channel and Publishing Events to a channel.