On Jan 28, 2012, at 8:21 AM, Allen Wirfs-Brock wrote:
>
> On Jan 27, 2012, at 10:15 PM, John-David Dalton wrote:
>
>> I noticed in the ES6 draft it states that host objects *do not* have
>> the [[NativeBrand]] internal property.
>> I think "do not have" should be reworded to "are not required to have".
>> This would allow existing inferences like
>> `{}.toString.call(window.opera) == '[object Opera]'`.
>>
>
> I probably need to be more explicit about host objects and add another step
> just before step 5
>
> If O is a host object, let tag be an implementation defined string value. The
> value may not be "Array", "Boolean", "Date", "Error", "Function", "JSON",
> "Math", "Number", "Object", "RegExp", and "String".
>
> Also, the definition of Host Object needs to be tighten up to make it clear
> that an object is only a host object if it has some "magical" behavior.
>
Yes, it's an old subtle terminological topic which is required to be mentioned
in the spec, I think it would be good.
In fact, if an object is completely conforming with the spec, it cannot be
distinguished from native objects -- regardless in which language it's written
(in JS itself or in a lower language).
Moreover, many "host" objects are implemented in JS itself -- e.g. some
standard libraries as in Node.js. I called them inefficiently as "native-host"
objects.
But from this viewpoint -- is this algorithm step is correct? I.e. window.opera
being as a native-host can nevertheless have as its [[NativeBrand]] values of
"Array", "Object", etc?
And a host object then becomes as "an object provided by a host environment and
has semantic differentiations from this specification".
(the only thing it's needed to consider is not to make it even more confused or
complicated).
Dmitry
> Finally, window.opera is really just a normal object it could use my proposed
> private name based mechanism to set its toString tag.
>
> Allen
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