Simple JS Event Bus

SimpleEventBus.js

    var EventBusClass = {};
  	EventBusClass = function() {
  		this.listeners = {};
  	};
  	EventBusClass.prototype = {
  		addEventListener: function(type, callback, scope) {
  			var args = [];
  			var numOfArgs = arguments.length;
  			for(var i=0; i<numOfArgs; i++){
  				args.push(arguments[i]);
  			}
  			args = args.length > 3 ? args.splice(3, args.length-1) : [];
  			if(typeof this.listeners[type] != "undefined") {
  				this.listeners[type].push({scope:scope, callback:callback, args:args});
  			} else {
  				this.listeners[type] = [{scope:scope, callback:callback, args:args}];
  			}
  		},
  		removeEventListener: function(type, callback, scope) {
  			if(typeof this.listeners[type] != "undefined") {
  				var numOfCallbacks = this.listeners[type].length;
  				var newArray = [];
  				for(var i=0; i<numOfCallbacks; i++) {
  					var listener = this.listeners[type][i];
  					if(listener.scope == scope && listener.callback == callback) {

  					} else {
  						newArray.push(listener);
  					}
  				}
  				this.listeners[type] = newArray;
  			}
  		},
  		hasEventListener: function(type, callback, scope) {
  			if(typeof this.listeners[type] != "undefined") {
  				var numOfCallbacks = this.listeners[type].length;
  				if(callback === undefined && scope === undefined){
  					return numOfCallbacks > 0;
  				}
  				for(var i=0; i<numOfCallbacks; i++) {
  					var listener = this.listeners[type][i];
  					if((scope ? listener.scope == scope : true) && listener.callback == callback) {
  						return true;
  					}
  				}
  			}
  			return false;
  		},
  		dispatch: function(type, target) {
  			var event = {
  				type: type,
  				target: target
  			};
  			var args = [];
  			var numOfArgs = arguments.length;
  			for(var i=0; i<numOfArgs; i++){
  				args.push(arguments[i]);
  			};
  			args = args.length > 2 ? args.splice(2, args.length-1) : [];
  			args = [event].concat(args);


  			if(typeof this.listeners[type] != "undefined") {
  				var listeners = this.listeners[type].slice();
  				var numOfCallbacks = listeners.length;
  				for(var i=0; i<numOfCallbacks; i++) {
  					var listener = listeners[i];
  					if(listener && listener.callback) {
  						var concatArgs = args.concat(listener.args);
  						listener.callback.apply(listener.scope, concatArgs);
  					}
  				}
  			}
  		},
  		getEvents: function() {
  			var str = "";
  			for(var type in this.listeners) {
  				var numOfCallbacks = this.listeners[type].length;
  				for(var i=0; i<numOfCallbacks; i++) {
  					var listener = this.listeners[type][i];
  					str += listener.scope && listener.scope.className ? listener.scope.className : "anonymous";
  					str += " listen for '" + type + "'\n";
  				}
  			}
  			return str;
  		}
  	};
  	var EventBus = new EventBusClass();
   


function myFunction(event) {
  console.log("myFunction type=" + event.type);
}
EventBus.addEventListener("my_function_event", myFunction);
EventBus.dispatch("my_function_event");