Use cases for WeakMap

Brendan Eich brendan at
Sun May 15 23:57:19 PDT 2011

On May 15, 2011, at 11:53 PM, Erik Corry wrote:

> 2011/5/16 Brendan Eich <brendan at>:
>> This is a good point too. Not sure we've considered a value -> value map carefully yet.
> A value->anything map is pretty easy to do with a normal JS object.
> function get(value) {
>  if (typeof(value) == 'number') return this["NUM" + value];
>  if (typeof(value) == 'string') return this["STR" + value];
>  ...
> }

Where's the 'object' case (excluding null)?

> Weakness makes no sense in this case since a value can never really be lost.

Weakness is still necessary for an object key if you want to avoid leaks and you don't need to enumerate.


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