Simple pubsub communication interface. Licence - do whatever.

API

on

alias: sub

pubsub.on( topic, callback )
pubsub.on( topic, callback, priority )
pubsub.on( topic, unsubscribeLabel, callback )
pubsub.on( topic, unsubscribeLabel, callback, priority )

Subscribe to a topic.

• topic [string] topic you're subscribing to
• unsubscribeLabel [string] can later be used for easier unsubscribing (see examples)
• callback [function] invoked after publishing to corresponding topic
• priority [number] callback invocation priority relative to other subscriptions for the same topic. Default is 10.

Returns the callback (useful when dealing with anonymous functions).

once

alias: subOnce

pubsub.once( topic, callback )
pubsub.once( topic, callback, priority )
pubsub.once( topic, unsubscribeLabel, callback )
pubsub.once( topic, unsubscribeLabel, callback, priority )

Subscribe to a topic.

Same as 'on' except the callback is invoked only once and subscription is automatically removed immediately after.

emit

alias: pub

pubsub.emit( topic, ...arguments )

Publish - invoke topic subscriptions.

• topic [string] topic whose subscriptions you're invoking
• arguments [any type] you can pass any number of arguments to subscription callbacks

off

alias: unsub

pubsub.off( callback )
pubsub.off( topic, callback )
pubsub.off( unsubscribeLabel )
pubsub.off( topic, unsubscribeLabel )

Remove subscriptions. If you don't pass a topic, all matching subscriptions will be removed across all topics.

• topic [string] topic you're unsubscribing from
• callback [function] remove all subscriptions that use this callback
• unsubscribeLabel [string] remove all subscriptions that have this label

Examples

Basic usage

Subscribe, then publish and pass some data

pubsub.on('userCreated', (age, email) => {
  console.log(age, email)
})

pubsub.emit('userCreated', 30, '[email protected]')
// 30, '[email protected]'

Subscribe once, publish

pubsub.once('boom', () => {
  console.log('BANG!')
})

pubsub.emit('boom')
// 'BANG!'
pubsub.emit('boom')
//

Subscribe, publish and unsubscribe

let callback = pubsub.on('boom', () => {
  console.log('BANG!')
})

pubsub.emit('boom')
// 'BANG!'
pubsub.emit('boom')
// 'BANG!'

pubsub.off('boom', callback)

pubsub.emit('boom')
//

In this example we used the anonymous function returned by 'on' to unsubscribe. You can also just use named functions.

Prioritized subscribers (use sparingly)

You can control topic callback invocation order by assigning a priority to your subscriptions.

pubsub.on('boom', () => {
  console.log('FIVE')
}, 5)

pubsub.on('boom', () => {
  console.log('ONE')
}, 1)

pubsub.on('boom', () => {
  console.log('TEN')
}, 10)

pubsub.emit('boom')
// 'TEN'
// 'FIVE'
// 'ONE'

This is generally a bad practice as it makes code harder to understand. It would be better to create multiple topics like beforeBoom, boom, afterBoom etc.

Unsubscribing via labels

Unsubscribe globally across all topics

pubsub.on('userCreated', 'userActions', () => { do stuff... })
pubsub.on('userUpdated', 'userActions', () => { do stuff... })
pubsub.on('userDeleted', 'userActions', () => { do stuff... })

pubsub.off('userActions')
// this will remove all three subscriptions

Unsubscribe scoped to a topic

pubsub.on('userCreated', 'userActions', () => { do stuff... })
pubsub.on('userUpdated', 'userActions', () => { do stuff... })
pubsub.on('userDeleted', 'userActions', () => { do stuff... })

pubsub.off('userCreated', 'userActions')
// this will remove only the first subscription

Subscribe, publish, unsubscribe with multiple topics

Simple example

pubsub.on('userCreated', () => {
  console.log('user created')
})

pubsub.on('userUpdated', () => {
  console.log('user updated')
})

pubsub.emit('userCreated userUpdated')
// 'user created'
// 'user updated'

More complex example with labels and some data

pubsub.on('userCreated userUpdated', 'label', (data) => {
  console.log('user created or updated', data.a)
})

pubsub.on('userDeleted', 'label', (data) => {
  console.log('user deleted', data.a)
})

pubsub.emit('userCreated userUpdated userDeleted', {a: 'yay!'})
// 'user created or updated', 'yay!'
// 'user created or updated', 'yay!'
// 'user deleted!', 'yay!'

pubsub.off('userCreated userUpdated userDeleted', 'label')
// remove all subscriptions

Emits - namespaced publish (you probably don't need this)

alias: pubs

I sometimes find it useful to visually namespace my topic names so I added some sugar.

If you use the 'emits' method and pass a topic name namespaced by ':' such as 'pageMounted:users', pubsub will emit two times. First 'pageMounted', then 'pageMounted:users'.

It will also pass 'users' string to the 'pageMounted' emit as the first argument. Other arguments will follow in their original order.

pubsub.on('pageMounted', (name) => {
  document.title = name
  analytics.track('pageview' {name: name})
  ...do other general page stuff...
})

pubsub.on('pageMounted:users', () => {
  getSomeExtraUserData()
  ...do stuff specific to users page...
})

pubsub.emits('pageMounted:users')

// this is the same as writing:

pubsub.emit('pageMounted', 'users')
pubsub.emit('pageMounted:users')

// if you want to change the order of topics add '-' to the beginning of topic name like this:

pubsub.emits('-pageMounted:users')

// this is the same as writing:

pubsub.emit('pageMounted:users')
pubsub.emit('pageMounted', 'users')

GL&HF