Le 31/12/2012 07:19, Boris Zbarsky a écrit :
On 12/30/12 1:20 PM, Claude Pache wrote:
FWIW, I used the fact that, in IE 8 & 9, innerHTML is conveniently a
configurable accessor found at Element.prototype (in IE8) or
HTMLElement.prototype (in IE9), for correcting a quirk of its setter,
by extracting it and replacing it with a corrected version.
Indeed, this is one of the major reasons properties are accessors in
WebIDL. It allows libraries to polyfill functionality as it's added
in specs (e.g. if the set of things that can be assigned to a property
changes, that may be possible to polyfill by hooking the setter).
I don't know if and how it would be possible if it was an own
property on each instance
It wouldn't be possible, in the proposals I've seen so far in this thread.
Polyfillability is an interesting criteria. Is
Object.getOwnPropertyDescriptor polyfillability important? Would a good
[[Get]]+[[Set]] polyfill be enough? By that I mean that as long as the
[[Get]]+[[Set]] behavior is good, maybe polyfilling a property by an
accessor is good enough?
I tend to consider data or accessor property as an implementation
detail. It's important to specify it in WebIDL for interoperability, but
authors should be worried of making the [[Get]]/[[Set]] protocol work
and use the rest of the tooling (low-level property descriptor stuff) to
make this work.
If necessary, WebIDL is free to add custom property descriptor
attribute. It could look like:
Object.defineProperty(webIDLObject, 'bla', {value: 25, webIDLType:
'long'})
And it would create an own property of type long (so subject to all
relevant WebIDL logic). I would prefer that innerHTML stay a
getter/setter, but it could be possible to describe it as an own
property and send out its logic through a property descriptor attribute.
Very heavy-weight, but technically possible. I prefer the getter/setter
solution.
David
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