On 10/29/10 4:50 AM, Peter van der Zee wrote:
What's the use case for weak maps? What would you do with it that currently impossible and why is the workaround (if any) problematic enough to warrant a weak map implementation?
One case this came up recently was for Firebug, Firebug wants to cache information about DOM Windows (the set of scripts compiled for that window, etc) and map from a Window to the information, but it obviously doesn't want to change the state of the Windows by adding properties, nor does it want to leak every single Window object.
There is no in-language workaround for this use case; we solved it in Gecko by adding special out-of-band API that assigns a numeric ID to each window and exposes that ID on an object that is not the window itself and which content doesn't have access to, so that Firebug can use the IDs as the keys in its map.
The use case generalizes, of course, to any situation where you want to store information for/about objects without sticking it on the object itself.
-Boris _______________________________________________ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
