EventBus

A generic multi-level event emitter with granular control over event emitting level.

Install

yarn add @magic8bot/event-bus

or

npm i @magic8bot/event-bus

API

Method	Return	Example
new EventBus	EventBus	const eventBus = new EventBus()
get	EventBus	eventBus.get('eventName')
		eventBus.get('eventName')('foo')
		eventBus.get('eventName')('foo')('bar')
emit	void	eventBus.emit(data)
		eventBus.get('eventName').emit(data)
		eventBus.get('eventName')('foo').emit(data)
listen	unlisten()	eventBus.listen(listenerFn)
		eventBus.get('eventName').listen(listenerFn)
		eventBus.get('eventName')('foo').listen(listenerFn)
		eventBus.get('eventName')('foo')('bar').listen(listenerFn)

Methods explained

new EventBus

Creates a new root event bus node.

eventBus.get(string)

Returns a new child node EventBus.

• Can be curried infinitely.

eventBus.emit(any)

Will emit an event to it's level and all descendant nodes.

eventBus.listen((any) => void)

Will listen to events on it's level and all ancestors leading to root.
The return value is an unlisten function. When invoked, it will stop this
listener from receiving any more events.

Examples

Basic

The most basic single level event bus.

import {} from '@magic8bot/event-bus'

const eventBus = new EventBus()

const emitter = eventBus.emit
const listener = eventBus.listen

listener((data) => {
  // ...Do something with data
})

listener((data) => {
  // ...Do something else with data
})

emitter({ foo: 'bar' })
emitter({ fizz: 'bang' })

2 level event bus (terse syntax)

A dual level tiered event bus.

• All root level events will bubble up.
• Events can be granular and be sent only into a specific level.

import {} from '@magic8bot/event-bus'

const eventBus = new EventBus()

const emitter = eventBus.emit
const listener = eventBus.listen

const eventBusL2 = eventBus.get('L2')
const emitterL2 = eventBusL2.emit
const listenerL2 = eventBusL2.listen

// Will onlt get events from `emitter`
listener((data) => {
  // ...Do something with data
})

// Will get events from `emitter` and `emitter -> emitterL2`
listenerL2((data) => {
  // ...Do something else with data
})

emitter({ foo: 'bar' })
emitterL2({ fizz: 'bang' })

2 level event bus (alternate syntax)

import {} from '@magic8bot/event-bus'

const eventBus = new EventBus()

// Will onlt get events from `eventBus`
eventBus.listen((data) => {
  // ...Do something with data
})

// Will get events from `eventBus` and `eventBus -> L2`
eventBus.get('L2').listen((data) => {
  // ...Do something else with data
})

eventBus.emit({ foo: 'bar' })
eventBus.get('L2').emit({ fizz: 'bang' })

Tree like event bus

A tree like tiered event bus.

• All root level events will bubble up.
• Events can be granular and be sent only into a specific level.
• Each level can act as another root

import {} from '@magic8bot/event-bus'

const eventBus = new EventBus()

// Will onlt get events from `eventBus`
eventBus.listen((data) => {
  // ...Do something with data
})

// Will get events from `eventBus` and `eventBus -> L2.1`
eventBus.get('L2.1').listen((data) => {
  // ...Do something else with data
})

// Will get events from `eventBus` and `eventBus -> L2.2`
eventBus.get('L2.2').listen((data) => {
  // ...Do more with data
})

// Will get events from `eventBus`, `eventBus -> L2.2`, and `eventBus -> L2.2 -> L3`
eventBus
  .get('L2.2')('L3')
  .listen((data) => {
    // ...Do even more with data
  })

eventBus.emit({ foo: 'bar' })
eventBus.get('L2.1').emit({ fizz: 'bang' })
eventBus.get('L2.2').emit({ blep: 'cat' })
eventBus.get('L2.2')('L3').emit({ derp: 'dog' })