Use cases for WeakMap

Rick Waldron waldron.rick at gmail.com
Sun May 15 11:20:57 PDT 2011


Thanks Brendan, I was looking for something that was representative of
Boris's use-case, but I appreciate the snippet none-the-less.

I should clarify my intentions; while your example is very straight forward,
it's also as ambiguous as the gist I had originally posted that Alex,
yourself and I shared a discussion on - only in that it doesn't illustrate
the behaviour of the weakmap that has had a nulled key, post-GC.

I'm coming at this from the perspective of an js application developer and
thinking  "how do I synthesize this into something that developers can
understand the benefit of and apply to real-world uses?", in short:
developer education/relations.

Either way, thanks again!

Rick


On Sun, May 15, 2011 at 2:02 PM, Brendan Eich <brendan at mozilla.com> wrote:

> On May 14, 2011, at 6:06 PM, Rick Waldron wrote:
>
> Boris,
>
> Would you mind sharing a piece of working code (as in, runs in the latest
> Firefox Nightly) that demonstrates your example in a real world scenario?
> This would be greatly appreciated
>
>
> javascript:k = {}; v = "hi"; w = WeakMap(); w.set(k, v); alert(w.get(k))
>
> just alerted "hi" in my slightly out of date tracemonkey-repo nightly
> build. There may be some javascript: URL stripping or blocking you have to
> get past, in which case use the code after the javascript: in the Web
> Console.
>
> /be
>
>
>
> Rick
>
> On Sat, May 14, 2011 at 8:55 PM, Boris Zbarsky <bzbarsky at mit.edu> wrote:
>
>> On 5/14/11 6:37 PM, Oliver Hunt wrote:
>>
>>> Can you provide a use case where you have an object key as the usual
>>> programming idiom?
>>>
>>
>> Attaching metadata to object without polluting the objects themselves.
>>
>> For example, Firefox extensions want to do this all the time for various
>> DOM objects (and especially Window).
>>
>> -Boris
>>
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