A DOM use case that can't be emulated with direct proxies

Kevin Reid kpreid at google.com
Wed Dec 12 12:42:15 PST 2012


On Wed, Dec 12, 2012 at 12:35 PM, David Bruant <bruant.d at gmail.com> wrote:

> I was a bit too strong in my statement, sorry. Let me rephrase: the
> internal [[Target]] can't be changed, but a proxy can emulate changing of
> "fake" target as long as what happens with this "fake" target doesn't
> involve invariant checking.
> That's the reason I was suggesting that WindowProxies could (maybe
> depending on how the object reference was obtained) throw whenever
> invariant checks are involved.
>

Exactly. So a user-defined switching proxy needs only to:
1. refuse to commit to any invariant (non-configurable property or
preventExtensions)
2. even if its switchable-target has an invariant, do not expose that
invariant (i.e. pretend each property is configurable)
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