On Sep 18, 2014, at 1:11 PM, Domenic Denicola wrote:
> From: es-discuss [mailto:es-discuss-boun...@mozilla.org] On Behalf Of Domenic
> Denicola
>
>> I'm just quoting Allen's gist. It's a base class whose constructor always
>> throws (in the gist, by doing `this = undefined`). Almost all DOM classes
>> are currently like this, for example.
>
> Actually, this is a really important point. Since HTMLElement is abstract
> (throws on construct in all cases), the *only* way of extending it is by
> doing `this = Object.create(new^.prototype)`. You *cannot* extend it with
> `this = new super()`, either implicitly or explicitly, since `new super()`
> throws.
>
> So if you want to extend HTMLElement, you will need `this =
> Object.create(new^.prototype)`, either implicitly or explicitly. (And I argue
> for implicitly.)
But that won't give you a real HTMLElement exotic object, if there is such a
thing, and won't initialize it properly.
But you can get around that problem if the HTMLElement constructor is defined
appropriately using this^:
class HTMLElement {
constructor(...args) {
if (this^ === HTMLElement) then throw new DOMError("can't create using
new");
if (this !== undefined) {
//assert: must have been called via new super()
this = privateAllocatedDOMElement();
//initialize newly allocated DOMElement
}
}
}
Allen
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