On: Experimental support for ECMAScript 6 Map and Set objects in Firefox 13

[program]

I really hope that Map and Set will be iterable as described here: http://wiki.ecmascript.org/doku.php?id=harmony:iterators otherwise, in my opinion, they will be pretty useless.

As an addendum it looks like that 'undefined' is a valid key:

   var m = new Map;
   m.set(undefined, 1);
   console.log(m.get(undefined));