Deferred Event Queue Patterns

angular service

'use strict';

angular.module('rallyApp')
  .service('EventQueue', function EventQueue($q) {
    var eventQueues = {};
    var listeners = {};

    var triggerEvent = function(queue, event, listener) {
      queue.splice(queue.indexOf(event), 1);
      listener.cb(event);
    };

    var checkListener = function(listener, channelName) {
      var queue = eventQueues[channelName];
      events.forEach(function(event) {
        triggerEvent(queue, event, listener);
      });
    };

    var checkListeners = function() {
      Object.keys(listeners).forEach(function(channelName) {
        listeners[channelName].forEach(function(listener) {
          checkListener(listener, channelName);
        });
      });
    };

    var ensureChannel = function(channelName, context) {
      if (typeof(context[channelName]) === 'undefined')
        context[channelName] = [];
      return context[channelName];
    };

    return {
      on: function(channelName, cb) {
        var channel = ensureChannel(channelName, listeners);
        channel.push({
          cb: cb
        });
        service.checkListeners();
      },
      queue: function(channelName, data) {
        var channel = ensureChannel(channelName, eventQueues);
        if (typeof(data) === 'undefined')
          data = {};
        channel.push(data);
        service.checkListeners();
      }
    };
    return service;
  });

angular shim

'use strict';

angular.module('rallyApp')
  .service('EventQueue', function EventQueue($rootScope) {
    var eventQueues = {};

    var ensureChannel = function(channelName, context) {
      if (typeof(context[channelName]) === 'undefined')
        context[channelName] = [];
      return context[channelName];
    };

    return {
      on: function(channelName, cb) {
        var events = ensureChannel(channelName, eventQueues);
        $rootScope.$on(channelName, function(event, eventData) {
          if (events.indexOf(eventData) > 0)
            events.splice(events.indexOf(eventData), 1);
          cb(event, args);
        });
        events.forEach(function(eventData) {
          $rootScope.$broadcast(channelName, eventData);
        });
      },
      queue: function(channelName, data) {
        if (typeof(data) === 'undefined')
          data = {};

        $rootScope.$broadcast(channelName, data);

        var channel = ensureChannel(channelName, eventQueues);
        channel.push(data);
      }
    };
    return service;
  });