On Aug 4, 2010, at 11:36 AM, Travis Leithead wrote:
> Sure.
>
> Not only does ES5's configurable: false property prevent deletion, but it
> also prevents changing a property from a field to an accessor and vice-versa,
> as well as changing the getter/setters of the property.
>
> So, the following wouldn't work if the "appendChild" property was
> configurable:false:
>
> Object.defineProperty(Node.prototype,
> "appendChild",
> { get: function() { /* custom getter replacement */ },
> set: function(x) { /* custom setter replacement */ }
> });
>
> ... which is the ES5 way of doing:
> Node.prototype.__defineGetter__("appendChild", function() { /* custom getter
> replacement */ });
> Node.prototype.__defineSetter__("appendChild", function(x) { /* custom setter
> replacement */ });
>
> So, configurable: false prevents users from replacing built-in properties
> with getter/setters. I think this is too restrictive, especially
> forward-looking considering how much the DOM is changing and evolving.
I don't see why you would want to do that. The common way to override the
behavior of DOM operations is:
Node.prototype.appendChild = function(node) { /* replacement function */ }
I think what you describe is not commonly done, or particularly useful.
Furthermore, prototype hacking is primarily used for additions, not
replacements, which are not impacted by this at all.
Likewise, I don't think it's common to want to add a setter for the window.Node
global interface object.
Regards,
Maciej
>
> -----Original Message-----
> From: Jonas Sicking [mailto:[email protected]]
> Sent: Tuesday, August 03, 2010 5:22 PM
> To: Travis Leithead
> Cc: Cameron McCormack; Sam Weinig ([email protected]); [email protected]
> Subject: Re: [WebIDL] interface objects and properties too restrictive?
>
> On Tue, Aug 3, 2010 at 4:57 PM, Travis Leithead <[email protected]> wrote:
>> Hey folks, just wondering what the justification behind the current
>> {DontDelete} semantics are in WebIDL 4.4 [1] and 4.5 (second bullet)
>> [2]. When our IE9 binding ported this to ES5, it translated to
>> "configurable: false", which completely destroyed the ability to set
>> accessors on the interface objects as well as operations (and in our
>> case, DOM accessors). Because of this, we actually don't mark our
>> interface objects OR operations/attributes as configurable: false,
>> rather configurable: true.*
>>
>> If this seems reasonable, I'd like to see the spec updated.
>
> Sorry, I'm not very updated on the differences between the ES3 and ES5
> worlds. Why does "configurable: false" destroyed the ability to set
> accessors? Can you give an example of a piece of script that doesn't work but
> which you'd like to work, and what you'd like it to do?
>
> / Jonas
>
>
