javascipt custom object and events [duplicate]

I ma trying to have my custom javascript objects be able to dispatch thier own events. I have this code exmaple. The problem is that events are duplicated when I create more than 1 object. Why is this hapenning?

(function() {
  var EventDispatcher = function() {

    var self = this;

    self.events = {};

    self.addEventListener = function(name, handler) {
      if (self.events.hasOwnProperty(name)) {
        self.events[name].push(handler);
      } else {
        self.events[name] = [handler];
      }
    };

    self.removeEventListener = function(name, handler) {
      if (!self.events.hasOwnProperty(name)) return;

      var index = self.events[name].indexOf(handler);
      if (index != -1) self.events[name].splice(index, 1);
    };

    self.fireEvent = function(name, args) {
      if (!self.events.hasOwnProperty(name)) return;

      if (!args || !args.length) args = [];

      var evs = self.events[name],
        l = evs.length;
      for (var i = 0; i < l; i++) {
        evs[i].apply(null, args);
      }
    };

  };

  window.EventDispatcher = EventDispatcher;
}(window));


(function(window) {
  "use strict"
  var PlaylistManager = function(data) {

    var self = this

    this.test = function() {
      self.fireEvent('PlaylistManager.COUNTER_READY', [{
        counter: "a"
      }]);
    }

  }

  PlaylistManager.prototype = new EventDispatcher();

  window.PlaylistManager = PlaylistManager;

}(window));


var _PlaylistManager = new PlaylistManager();

_PlaylistManager.addEventListener('PlaylistManager.COUNTER_READY', function(e) {
  console.log('COUNTER_READY')

})


var _PlaylistManager2 = new PlaylistManager();

_PlaylistManager2.addEventListener('PlaylistManager.COUNTER_READY', function(e) {
  console.log('COUNTER_READY 2')

})

_PlaylistManager.test()

_PlaylistManager2.test()

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