Proxy.isProxy (Was: using Private name objects for declarative property definition.)

Tom Van Cutsem at
Wed Jul 13 01:23:53 PDT 2011

Perhaps Proxy.isProxy was used merely as an example, but wasn't the
consensus that Proxy.isProxy is not needed? Dave pointed out that it breaks
transparent virtualization. Also, there is Object.isExtensible which always
returns |true| for (trapping) proxies. That means we already have "half" of
Proxy.isProxy without exposing proxies: if !Object.isExtensible(obj), obj is
guaranteed not to be a proxy.


2011/7/9 Brendan Eich <brendan at>

> Also the Proxy.isTrapping, which in recent threads has been proposed to be
> renamed to Proxy.isProxy or Object.isProxy.
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