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

Brendan Eich brendan at
Wed Jul 13 09:28:28 PDT 2011

On Jul 13, 2011, at 1:23 AM, Tom Van Cutsem wrote:

> Perhaps Proxy.isProxy was used merely as an example,

That's right, it was one of several in seeking for naming conventions, and deeper distinctions among type-testing predicates. Not to worry -- I agree we should remove it.


> 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.
> Cheers,
> Tom
> 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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