// written by Dean Edwards, 2005

 // with input from Tino Zijdel, Matthias Miller, Diego Perini

 // http://dean.edwards.name/weblog/2005/10/add-event/

 function addEvent(element, type, handler) {

     if (element.addEventListener) {

         element.addEventListener(type, handler, false);

     } else {

         // assign each event handler a unique ID

         if (!handler.$$guid) handler.$$guid = addEvent.guid++;

         // create a hash table of event types for the element

         if (!element.events) element.events = {};

         // create a hash table of event handlers for each element/event pair

         var handlers = element.events[type];

         if (!handlers) {

             handlers = element.events[type] = {};

             // store the existing event handler (if there is one)

             if (element["on" + type]) {

                 handlers[0] = element["on" + type];

             }

         }

         // store the event handler in the hash table

         handlers[handler.$$guid] = handler;

         // assign a global event handler to do all the work

         element["on" + type] = handleEvent;

     }

 };

 // a counter used to create unique IDs

 addEvent.guid = 1;

 function removeEvent(element, type, handler) {

     if (element.removeEventListener) {

         element.removeEventListener(type, handler, false);

     } else {

         // delete the event handler from the hash table

         if (element.events && element.events[type]) {

             delete element.events[type][handler.$$guid];

         }

     }

 };

 function handleEvent(event) {

     var returnValue = true;

     // grab the event object (IE uses a global event object)

     event = event || fixEvent(((this.ownerDocument || this.document || this).parentWindow || window).event);

     // get a reference to the hash table of event handlers

     var handlers = this.events[event.type];

     // execute each event handler

     for (var i in handlers) {

         this.$$handleEvent = handlers[i];

         if (this.$$handleEvent(event) === false) {

             returnValue = false;

         }

     }

     return returnValue;

 };

 function fixEvent(event) {

     // add W3C standard event methods

     event.preventDefault = fixEvent.preventDefault;

     event.stopPropagation = fixEvent.stopPropagation;

     return event;

 };

 fixEvent.preventDefault = function() {

     this.returnValue = false;

 };

 fixEvent.stopPropagation = function() {

     this.cancelBubble = true;

 };