Must built-in prototypes also be valid instances? (Was: Why DataView.prototype object's [[Class]] is "Object"?)

Brendan Eich brendan at
Mon Oct 1 13:06:05 PDT 2012

Erik Arvidsson wrote:
> On Mon, Oct 1, 2012 at 3:30 PM, Brendan Eich<brendan at>  wrote:
>> Erik Arvidsson wrote:
>>> I'm with Allen, Andreas and others that the craziness needs to stop.
>> Which craziness?
> That the prototype of the constructor needs to be a special case of
> the instances created by the constructor.
> Today, both "new Date" and "Date.prototype" are date objects. I think
> this just makes things more complicated for no apparent gain.

Yes, and it makes that side channel that vexed Mark and SES (Caja).

Can we change incompatibly? Rick just asked what code relies on builtins 
being firstborns. No one relies on degenerate firstborns except by 
toString "tag testing".


More information about the es-discuss mailing list