Attribute defaults for Object.defineProperty

Neil Mix nmix at
Thu Aug 21 07:37:39 PDT 2008

writable: can be written to
enumerable: can be enumerated
flexible: can be flexed?

how about configurable?

On Aug 20, 2008, at 5:31 PM, Allen Wirfs-Brock wrote:

>> From: Brendan Eich [mailto:brendan at]
>> Sent: Wednesday, August 20, 2008 11:25 AM
> [snip]
>> Hi Allen, could you remind me and a few others who were wondering
>> yesterday (sorry I don't remember -- it's in minutes, somewhere) why
>> [[Deletable]] was not chosen instead of [[Flexible]]? Thanks.
> The reason for not using "deletable" was originally explained in the  
> message below.  I believe that at one of the phone meetings after  
> Oslo we briefly discussed changing it back to "dynamic" or possibly  
> something else but the consensus was to stick with "flexible".
>> -----Original Message-----
>> From: es3.x-discuss-bounces at [mailto:es3.x-discuss-
>> bounces at] On Behalf Of Allen Wirfs-Brock
>> Sent: Thursday, June 26, 2008 1:39 PM
>> To: es3.x-discuss at x-discuss; es4-discuss at es4-
>> discuss
>> Subject: RE: "dynamic" attribute nomenclature
>> At today's ES 3.1 conference call (see
>> we agreed to use the term "Flexible" for the property attribute that
>> we recently had been calling "Dynamic" and which subsumes the
>> DontDelete attribute.
>> From: Allen Wirfs-Brock
>> Sent: Wednesday, June 25, 2008 10:37 AM
>> To: Lars Hansen; Mark S. Miller
>> Cc: es3.x-discuss at x-discuss
>> Subject: "dynamic" attribute nomenclature
>> In Lars's feedback on the the June 11, ES3.1 draft he said:
>> p26 8.6.1.  (And throughout the spec) The meaning of "dynamic" in ES4
>> is something else (it means a non-fixture property).  It would  
>> probably
>> reduce confusion if the property name Deletable were used here, as I
>> though we had agreed previously.
>> Dynamic as currently used in ES3.1 means more than just Deletable, it
>> also means that the property attributes (including the Dynamic
>> attribute) can be modified and that it can be transformed  between
>> being a data and procedural property. Hence, the name Deletable seems
>> to imply something too narrow.
>> Playing around with the thesaurus, the best "positive, active term  
>> that
>> I could find that seems to be a reasonable description of this
>> semantics is:
>>      Alterable
>> (other, perhaps less satisfy or otherwise unacceptable alternatives
>> include: changeable, mutable, modifiable, flexible, amendable)
>> Note this would mean  that data properties would expose properties
>> named Writable and Alterable.  My sense is that there is enough
>> conceptual  distance between those terms that there won't be too much
>> confusion.
>> Thoughts??
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