I think the problem here is that there's too much syntactic sugar in
sessionStorage/localStorage (this is more feedback to HTML5 or WebIDL,
and maybe Hixie or others could help to address it).
I can easily replace the object (window.sessionStorage={}), but I
can't be told when my sessionStorage is decorated by a new property,
because that's not something which is available to JS (gecko has
__noSuchMethod__, but there's no watch(sessionStorage, "*", feedback).
If there was a way for js objects to be told about property writes
then for the most part, they could replace a host's
sessionStorage/localStorage with their own object and do what they
need.
Today, if the HTML5 sessionStorage/localStorage objects relied on
(sugar-free) methods only, they wouldn't have a problem. -- No, I'm
not advocating this.
