Dispatcher pub/sub pattern

dispatcher.js

var Dispatcher = (function() {
  var instance
  var subscribers

  var reset = function () {
    subscribers = {}
  }
  
  var unsubscribe = function (type, handler, context) {
    context = context || null

    subscribers[type] = subscribers[type].filter(function (subscriber) {
      return subscriber.handler !== handler && subscriber.context !== context
    })
  }

  var subscribe = function (type, handler, context) {
    context = context || null

    if (!subscribers[type]) {
      subscribers[type] = []
    }

    var subscriber = {
      handler: handler,
      context: context
    }

    subscribers[type] = subscribers[type].concat([subscriber])
    
    return function () {
      unsubscribe(type, handler, context)
    }
  }
  
  var publish = function (type, data) {
    subscribers[type].forEach(function (subscriber) {
      subscriber.handler.call(subscriber.context, data)
    })
  }
    
  var create = function () {
    reset()

    return Object.defineProperties({}, {
      subscribe: {
        value: subscribe
      },
      publish: {
        value: publish
      }
    })
  }

  return function () {
    if (!instance) {
      instance = create()
    }

    return instance
  }
})()

var dispatcher = Dispatcher()

var unsubscribe = dispatcher.subscribe('event.name', function (data) {
    ...
    code
    ...
})

unsubscribe()