Bus-JS

Bus-JS is a simple library which offers a simple implementation of an event bus to structure your code around the publish-subscribe pattern. The following code snippets show, what functionality the library offers, and how it should be used.

Bus

A Bus is an object to which a function may subscribe, unsubscribe, and which can publish data to its subscribers. So, the usage of a Bus may look as follows:

const { Bus } = require('@opdime/bus');

const bus = new Bus();

function someSubscriber(message) {
  console.log('bus-message payload:', message.payload);
}

bus.subscribe(someSubscriber);

bus.publish({
  payload: 'a bus message!'
});

A Bus subscriber will receive an IBusMessage as its first argument. Such a message consists of a payload and an optional channel. The exact TypeScript definition of an IBusMessage object looks as follows:

export interface IBusMessage {
  readonly channel?: string;
  readonly payload: any;
}

The publish method of the Bus expects an IBusMessage to be passed as its only argument. That exact message is then going to be passed to each of the subscribers of the Bus. Note that you should not modify the message, because it is going to be the same referenced object for each subscriber!

Each of the methods of a Bus returns the instance on which the method has been called. This enables you to set up a multitude of subscribers for a Bus in one chained call.

BusManager

The BusManager makes it easy to use multiple Buses in your application which are bound to specific channels.

BusManager.getChannelBus(channel)

With this method, the BusManager will may the Bus which has been created for this channel. Note that this function potentially return undefined if no bus is registered on the given channel!

BusManager.channel(channel)

This method guarantees to return a Bus. In case you want to get the Bus of a channel which has not been registered, it will be created.

BusManager.publish(message)

This method accepts an object which implements the interface IBusMessage. The provided message is going to be sent to each of the global subscribers. In case a channel has been defined in the message, that provided channel bus will then send the message on to its subscribers.