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[DOM4] EventTarget as first class citizen

From: Marcos Caceres <w3c@marcosc.com>
Date: Thu, 23 Feb 2012 11:21:07 +0000
To: public-webapps <public-webapps@w3.org>
Message-ID: <33467E275BEE4E1CAB6B67840D0E20BF@marcosc.com>
Hi,  
Would it be possible for DOM4 to define a way for user objects to be able to extend EventTarget (as in Object.create(EventTarget))?



The use case: give the ability to create objects that can dispatch events using native means… instead of hacking around it like so:  

var obj = Object.create(null);
var dispatcher = document.createElement("x-EventDispatcher");  

//implement EventTarget interface on obj  
Object.defineProperty(obj, "addEventListener", {
value: function(type, callback, capture){
dispatcher.addEventListener(type, callback, capture);  
}
});

Object.defineProperty(obj, "removeEventListener", {
value: function(type, callback, capture){
dispatcher.removeEventListener(type, callback, capture);  
}
});

Object.defineProperty(obj, "dispatchEvent", {
value: function(e){
dispatcher.dispatchEvent(e);  
}
});



var e = document.createEvent('CustomEvent');
e.initEvent("myEvent", false, false, null);  
dispatcher.dispatchEvent(e);  



Also, AFAIK, all JS frameworks have implemented custom ways of handling events and how they are dispatched, so clearly its a desired part of the platform. For example:

http://developer.yahoo.com/yui/docs/YAHOO.util.CustomEvent.html
http://api.jquery.com/category/events/event-object/
http://dojotoolkit.org/reference-guide/quickstart/events.html
  
Developers have also built their own:
http://www.nczonline.net/blog/2010/03/09/custom-events-in-javascript/

Other solutions fire at the document, which means registering listeners on an object that is not the one that needs to receive the event:
http://tiffanybbrown.com/2011/10/12/dispatching-custom-dom-events/

So, together with CustomEvents provided by the platform, it would be nice to have a custom EventTarget to fire those things at :)   

Kind regards,
Marcos  
--  
Marcos Caceres
Received on Thursday, 23 February 2012 11:21:41 GMT

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