Should host objects be able to have [[Class]] "Function", "Array" etc.?

Mike Shaver mike.shaver at
Sat Nov 15 05:19:34 PST 2008

2008/11/14 Maciej Stachowiak <mjs at>:
> Specifically, we expose a "filter" property on CSSStyleDeclaration, in
> support of the SVG filter CSS property. However, many sites test for
> "filter" to detect support for MSIE's proprietary "filter" property, which
> sadly has the same name but completely incompatible syntax. Thus, we return
> this kind of magical undetectable string so if tests don't detect us as IE.
> It works basically the same ways as Mozilla's undetectable document.all,
> which we also support.

Our undetectable document.all works by returning a different value
from the property access depending on whether it's a "detecting" use,
like |if (document.all)| -- we don't use a magic falsy object (which I
think is a violation of E262, but I'd have to dig into the ToBoolean
bits to be sure).


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