On Fri, Nov 11, 2011 at 3:28 PM, Irakli Gozalishvili <rfo...@gmail.com> wrote: > I really need to know why WeakMaps don't accept primitives as keys, can > anyone please reply ?
It’s because WeakMaps are intended to drop values if the key is garbage collected. A WeakMap guarantees that it will drop its value if it becomes provably inaccessible. This works for non-primitive keys because we can guarantee that once an object has been garbage collected, no future object can be created that would have been identical to it, making the value inaccessible. Once a primitive value like 1 or the string "abc" has been garbage collected, it is trivial to construct a new value that is identical to the original key, so we could never implicitly garbage collect the value corresponding to a primitive key. Mark Miller has proposed a strong variation of WeakMap, simply Map, that would serve well in cases where items are explicitly collected. http://wiki.ecmascript.org/doku.php?id=harmony:simple_maps_and_sets As I recall, a variant of Map was considered in the ES4 timeline as well. Kris Kowal _______________________________________________ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
