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Re: All ECMAScript attributes should be non-configurable

From: Brendan Eich <brendan@mozilla.org>
Date: Fri, 23 Sep 2011 17:58:41 -0700
Cc: public-script-coord@w3.org
Message-Id: <740E6180-1B0F-42E1-A117-C4BE5C47DD09@mozilla.org>
To: David Bruant <david.bruant@labri.fr>
On Sep 23, 2011, at 5:54 PM, David Bruant wrote:

> Le 24/09/2011 02:52, Brendan Eich a écrit :
>> On Sep 23, 2011, at 3:53 PM, David Bruant wrote:
>> 
>>> Currently, on Chrome and Opera (12), event attributes are configurable
>>> own properties (data in the former, accessor in the latter).
>>> Consequently, the freedom to prevent all events to have a "type" or
>>> "target" attribute doesn't exist by design.
>>> Do anyone miss that freedom? In other words, are there use cases of
>>> wanting this freedom at all or is it just a side-effect of putting
>>> properties on the prototype and defaulting to configurable=true because
>>> a choice has to be made?
>> The "own" vs. prototype design is intentional. The non-configurable is too.
> What is the rational behind each of these decisions?

AIUI, "own" costs a direct property per instance, reified. "prototype" obviously does not.

Sorry, I meant to write "configurable", not "non-configurable". Not sure why that's there. A non-configurable prototype property could not be deleted, which would remove the destroy-the-world hazard. It could still be shadowed, but not by assignment -- only by Object.defineProperty.

/be
Received on Saturday, 24 September 2011 00:59:08 UTC

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