Attribute defaults for Object.defineProperty

Allen Wirfs-Brock Allen.Wirfs-Brock at
Wed Aug 20 15:31:01 PDT 2008

> From: Brendan Eich [mailto:brendan at]
> Sent: Wednesday, August 20, 2008 11:25 AM
> 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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