[whatwg] Exposing EventTarget to JavaScript

Maciej Stachowiak mjs at apple.com
Fri Apr 24 13:29:16 PDT 2009

On Apr 24, 2009, at 11:29 AM, Aaron Boodman wrote:

> I like the basic idea, but I think drawing too much inspiration from
> DOM events is a bad idea. What does it mean to "capture" a pure JS
> event?

There's really two aspects to the DOM event model. One is the basic  
addEventListner / dispatchEvent mechanism, which allows objects to  
have event listeners attached. The other is the bubble/capture event  
flow in the DOM tree. It can make sense for an object to be an  
EventTarget without participating in bubble/capture, because it is not  
part of the DOM document tree. An example of this is XMLHttpRequest.

> Further, the DOM event model has problems. It would be nice if
> events were first-class, not strings. It would be more idiomatic JS, I
> would argue, to do someObject.onClick.add(<handler>).

It's a bit late in the game to change the DOM itself to work that way.  
And having some other event mechanism that works like this, while DOM  
events continue to work as they do, would be confusing I think. One  
advantage to string event names is that users of the DOM can invent  
custom event names at will. In addition, it is possible to register  
for events that are not supported without having to do feature  
testing. There are certainly downsides to the design but it is not  
without precedent.


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