If you want to self-host Date objects in JS you can use a WeakMap to store the
[[Value]] for each Date object (similar to private names, the Date object is
the key). The same goes for self-hosted DOM implementations (the content-facing
wrapper is the key used to look up the internal object holding the underlying
DOM node state).
Andreas
On May 14, 2011, at 3:37 PM, Oliver Hunt wrote:
> It's not that they're impossible, it's that they all reduce to a strong map
> with automatic deletion, rather than "WeakMap".
>
> Take any form of weak cache, say for example you want to cache the object
> representation that's the result of an XHR (or some such)
>
> eg. you want to do
>
> function getObject(url) {
> var result = myCache.get(url);
> if (result)
> return result;
> result = Object.freeze(JSON.parse(loadURLWithSynchXHR(url).responseText));
> myCache.set(url, result);
> return result;
> }
>
> Except you this doesn't work, because the map needs to have an object key, so
> the string is not allowed, we have to do new String(url) or some such as the
> key, so for a use case like this we need a map from string primitive to
> String object, so making the map a strong map.
>
> Can you provide a use case where you have an object key as the usual
> programming idiom?
>
> --Oliver
>
> On May 14, 2011, at 3:25 PM, Andreas Gal wrote:
>
>>
>> Can you describe those common use cases, and how they are impossible with
>> the current specification?
>>
>> Andreas
>>
>> On May 14, 2011, at 3:05 PM, Oliver Hunt wrote:
>>
>>> The more I read the WeakMap spec, the more it seems to prevent the common
>>> use cases I know of. Could someone give a few examples of problems the
>>> current weakmap spec solves?
>>>
>>> --Oliver
>>>
>>> _______________________________________________
>>> es-discuss mailing list
>>> [email protected]
>>> https://mail.mozilla.org/listinfo/es-discuss
>>
>
_______________________________________________
es-discuss mailing list
[email protected]
https://mail.mozilla.org/listinfo/es-discuss
