ECMA TC 39 / W3C HTML and WebApps WG coordination

Brendan Eich brendan at mozilla.com
Fri Sep 25 17:08:45 PDT 2009


On Sep 25, 2009, at 4:57 PM, Maciej Stachowiak wrote:

> On Sep 25, 2009, at 1:18 PM, Brendan Eich wrote:
>
>> So if you are doing more ArrayLike interfaces, let's keep talking.  
>> Don't let at least my catchalls-considered-harmful statements stop  
>> progress on ArrayLikes.
>
> Perhaps when catchalls are considered for ECMAScript, there could b  
> a way to encapsulate the specific pattern of index access, so you  
> can have magical getters and setters for all index properties  
> (integer numbers in range to be an array index) without having to  
> install a full catchall for all properties.

Good point -- implementing array-likes via catchalls has been on our  
minds since the ES4 "meta" days [1], although we never split hooks  
based on property name being non-negative (possibly also <= 2^32 - 1  
-- or is it <= 2^32 - 2?!).

With WebIDL folks' help we will probably take down ArrayLike first,  
without going whole-hog for catchalls. The "catchalls climb the meta  
ladder" problem is more profound than the index/length magic (even the  
awful uint32 domain) of array-likes. I agree with Waldemar, we should  
make progress on array-likes without getting hung up on catchalls.

/be

[1] http://wiki.ecmascript.org/doku.php?id=proposals:catchalls


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