Catch-all proposal based on proxies

Mark S. Miller erights at google.com
Thu Dec 10 16:44:09 PST 2009


On Thu, Dec 10, 2009 at 4:42 PM, Mark S. Miller <erights at google.com> wrote:

> On Wed, Dec 9, 2009 at 11:26 PM, Mike Samuel <mikesamuel at gmail.com> wrote:
>
>> On the climbing the meta, I'd like to understand how this might
>> interact with other proposals.
>>
>> get - already can execute arbitrary code due to getters
>> set - already can execute arbitrary code due to setters
>> in - cannot for non host objects
>> delete - cannot for non host objects
>> enumerate - cannot for non host objects
>>
>
> By the currently proposed taxonomy at <
> http://wiki.ecmascript.org/doku.php?id=strawman:proxies#interaction_of_external_methods_and_proxies>,
> all the above are base-level operations. The list at <
> http://wiki.ecmascript.org/doku.php?id=strawman:proxies#climbing_the_meta_ladder>
> explains that all the above can cause user code to execute whereas the last
> three, as you point out, currently cannot.
>
>
>
>> hasOwnProperty - cannot for non host objects
>>
>> Incidentally, is Object.prototype.hasOwnProperty(myProxy)
>> O(myProxyHandler.keys().length) for proxies?  This seems bad since a
>> for (in) loop that filters out non-own properties would be O(n**2) on
>> top of the loop body.
>>
>
> By the current taxonomy, Object.prototype.hasOwnProperty(myProxy) is
> meta-level and always returns false on a trapping proxy, revealing that it
> does not actually have any own properties.
>
> Arrg! That should be Object.prototype.hasOwnProperty.call(myProxy, name).
aProxy.hasOwnProperty(name) will of course trap as you'd expect, and so is
base level.



>
> --
>    Cheers,
>    --MarkM
>



-- 
   Cheers,
   --MarkM
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