Use cases for WeakMap

Brendan Eich brendan at mozilla.com
Sun May 15 11:02:34 PDT 2011


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just alerted "hi" in my slightly out of date tracemonkey-repo nightly build.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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