On Mar 18, 2008, at 11:06 PM, Cameron McCormack wrote:
Travis Leithead:
I can think of some interesting use cases for implementing [[call]]
on an interface object... I'd prefer to leave it unspecified at best.
OK.
I agree with Hixie on the point of specifying the behavior of typeof,
and to me typeof HTMLDocument == 'function' makes sense, since I
think
of these as 'constructor objects' (even if they don't allow object
construction in some cases).
But if you want ‘typeof HTMLDocument == 'function'’, then you would
need to mandate [[Call]] being implemented on the interface object,
since ECMA-262 says that the typeof operator returns 'function' only
if
the object implements [[Call]]. And then if you require [[Call]] to
be
implemented, then you’d need to say what that function would do.
ECMA-262 actually allows typeof to return anything at all for host
objects (which all of the DOM binding objects are). So it would not be
an ECMA-262 violation, technically, for an uncallable object to give
typeof == 'function', but I do think it would be a bad idea.
In WebKit we currently follow the ECMA-262 callability-based approach
even for host objects, but not all web engines do. For example, I
believe that in Trident, NodeLists are callable but give a typeof
result of 'object' instead of 'function'.
Regards,
Maciej
