giveMeAnEventBus

Feeling down? No need to inject yourself with dependencies, just call 1-800-giveMeAnEventBus today. The event bus will arrive immediately and you can subscribe to all of the latest news. You can even publish your own stories.

And that’s not all. If you provide the magic key¹, you can even communicate with your friends in neighboring tabs.

const giveMeAnEventBus = (() => {
  let eventBusId = 0

  return (key=null) => {
    eventBusId++
    let subscribers = []
    let subscriberId = 0

    if(key) {
      window.addEventListener('storage', (e) => {
        if(e.key === key) {
          try { var value = JSON.parse(e.newValue) }
          catch(err) { return }
          publish(value.payload, false)
        }
      })

      setTimeout(() => {
        const initialValues = JSON.parse(localStorage.getItem(key))
        if(initialValues) {
          publish(initialValues.payload, false)
        }
      }, 0)
    }


    const unsubscribe = (handle) => {
      if(handle.eventBusId === eventBusId) {
        for(var i=0, l=subscribers.length; i < l; i++) {
          if(subscribers[i].subscriberId === handle.subscriberId) {
            subscribers.splice(i, 1)
            return
          }
        }
      }
    }

    const subscribe = (cb) => {
      subscriberId++
      subscribers.push({cb, subscriberId})
      let handle = { subscriberId, eventBusId }
      handle.unsubscribe = () => unsubscribe(handle)
      return handle
    }

    let eventId = 0
    const publish = ((event, persist=true) => {
      eventId++
      subscribers.forEach(s => s.cb({eventId, payload: event}))
      if(persist) {
        localStorage.setItem(key, JSON.stringify({payload: event, nonce: new Date()}))
      }
    }

    return { subscribe, unsubscribe, publish }
  }
})()