Cameron McCormack wrote:
> This is probably not what browsers do in practice, though. For example,
> Opera 9 has an addEventListener method directly on the Node interface
> prototype object
On 06/06/07, Boris Zbarsky <[EMAIL PROTECTED]> wrote:
What Gecko does is to put all properties for all the interfaces an object
implements onto the "closest" prototype object. So if you have a <div>,
HTMLDivElement.prototype will have all the properties the <div> is supposed to
have defined directly on it.
Is this the reason for:
var
div=document.createElement('div'),
span=document.createElement('span'),
text=document.createTextNode('What am I?');
Function.prototype.call.call(div.appendChild,span,text);
text.data+='\r\n'+text.parentNode.tagName;
failing with an uncaught exception in Gecko but not in any other browser?
With the following modification it succeeds with matching behaviour to
Presto and WebKit:
var
dd=document.createElement('dd'),
dt=document.createElement('dt'),
text=document.createTextNode('What am I?');
Function.prototype.call.call(dd.appendChild,dt,text);
text.data+='\r\n'+text.parentNode.tagName;
If so, is there any possibility of making that work?
I can understand not allowing e.g. applying the same appendChild
implementation to work on both Element and Attr objects, but not
allowing it on other element objects seems a bit limiting to me.
The prototype chain in Gecko basically follows the inheritance model in the DOM
spec: HTMLDivElement.prototype.[[Prototype]] === HTMLElement.prototype, etc.
Things like EventTarget are off to the side somewhere as in your imagined way to
handle it.
As a result, given a <div> object (call it "div"),
div.[[Prototype]] === HTMLDivElement.prototype
HTMLDivElement.prototype.[[Prototype]] === HTMLElement.prototype
div.appendChild === HTMLDivElement.prototype.appendChild
are all true, while
div.appendChild === HTMLElement.prototype.appendChild
is false. As a result, to change what the appendChild of a <div> is you have to
change it on HTMLDivElement.prototype.
Is there any compelling reason why
HTMLElement.prototype.appendChild === HTMLDivElement.prototype.appendChild
isn't true in Gecko? I.e. is there a good reason to not use the same
implementation of the function on all Element derived interfaces even
if it's located on different interface objects?
Of course all of this is subject to change, and in fact is likely to change some
time in the not too distant future.
To be honest, do we really think that specifying the exact prototype chain is
desirable? How likely are UAs to rework the mappings between their native code
and ECMAScript to follow said spec?
Well, I think developers are more interested in the prototype
hierarchy actually working for augmenting browsers as well as
Function.prototype.call and Function.prototype.apply actually working
on DOM methods in a natural way for ES than they are in any specific
prototype hierarchy.
--
David "liorean" Andersson
