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

Tom Van Cutsem at
Wed Nov 12 08:23:11 PST 2014

I agree with your sentiment. I have previously advocated that Array.isArray
should be transparent for proxies. My harmony-reflect shim explicitly
differs from the spec on this point because people using the shim
spontaneously reported this as the expected behaviour and thought it was a
bug that Array.isArray didn't work transparently on proxies.

As far as I can remember, the argument against making Array.isArray
transparent is that it's ad hoc and doesn't generalize to other types /
type tests. My opinion is that array testing is fundamental to core JS and
is worth the exception.


2014-11-12 17:04 GMT+01:00 Axel Rauschmayer <axel at>:

> The subject is a SpiderMonkey bug.
> Is that really desirable? Doesn’t it invalidate the Proxy’s role as an
> interceptor?
> --
> Dr. Axel Rauschmayer
> axel at
> _______________________________________________
> es-discuss mailing list
> es-discuss at
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