Array.isArray(new Proxy([], {})) should be false (Bug 1096753)

Brendan Eich brendan at
Fri Nov 14 12:36:07 PST 2014

Tom Van Cutsem wrote:
>     No really, it was a way to expose a test of the [[Class]] internal
>     property.  That test wasn't dependent upon the [[Prototype]] chain.
> I think what Domenic was saying is that Array.isArray used such a test 
> *because* instanceof Array didn't work reliably cross-realms. I too 
> vaguely recollect that reliable cross-realm "instanceof Array" testing 
> was a primary motivation for Array.isArray.

Yes, that was Crock's stated motivation as I recall. Here's a 2003-era 
post from Doug:!msg/comp.lang.javascript/XTWYCOwC96I/70rNoQ3L-xoJ


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