Type of property names, as seen by proxy traps

Andreas Rossberg rossberg at google.com
Thu Jul 7 11:52:20 PDT 2011


On 7 July 2011 19:35, David Bruant <david.bruant at labri.fr> wrote:
>> No, with the current keys default trap (calling
>> this.getOwnPropertyNames()) there is no double conversion. Only one at
>> the exit of the keys trap. There would be 2 conversions if the "keys"
>> trap had the proxy argument (based on
>> http://wiki.ecmascript.org/doku.php?id=strawman:handler_access_to_proxy)
>> and if internally, the default keys trap was calling
>> "Object.getOwnPropertyNames(proxy)" (which would call the trap and do
>> type coercion).
>>
>> But the current implementation and a type coercion only when going out
>> of traps would do double-conversion.
> "not". "would not do double-conversion", sorry.

I thought the fix we were discussing was changing the `keys' default trap from

keys: function() {
  return this.getOwnPropertyNames().filter(
    function (name) { return
this.getOwnPropertyDescriptor(name).enumerable }.bind(this));
}

to something along the lines of

keys: function() {
  return this.getOwnPropertyNames().filter(
    function (name) { return this.getOwnPropertyDescriptor('' +
name).enumerable }.bind(this));
}

That would fix passing non-strings to the getOwnPropertyDescriptor
trap, but introduce double conversions when you invoke Object.keys.
I'm not sure what alternative you are proposing now.

/Andreas


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