Catch-all proposal based on proxies

Mark S. Miller erights at
Thu Dec 10 20:30:56 PST 2009

On Thu, Dec 10, 2009 at 6:42 PM, Maciej Stachowiak <mjs at> wrote:

> On Dec 10, 2009, at 5:09 PM, Mike Samuel wrote:
> 2009/12/10 Mark S. Miller <erights at>:
> 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.
> Hmm.  So a proxy of an object cannot be used as a drop-in replacement
> for that object with any code that uses own property loops like
>   for (var k in o) if (, k)) ...
> ?
> That seems to make it less useful.
> It would also make this mechanism unsuitable for building emulations of DOM
> objects that have catchall properties in pure ECMAScript. Is that a design
> goal for this mechanism?

Hi Maciej, I agree that it is a problem. Tom & I are currently discussing
what to do about it. But I don't understand your description above. What
does "DOM objects that have catchall properties in pure ECMAScript" mean?

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