Access root domain's localStorage from subdomain

Question

EDIT:

For the sake of simplicity:

I've got a simple UserJS script (FF/Chrome: Greasemonkey, Opera: built-in) that fixes some issues on website I'm using quite often. The problem is that I need to store some data between different requests. My first attempt was LocalStorage but it fail when it came to work with subdomains: www.domain.com and subdomain.domain.com (unfortunately root-domain is subdomain in fact - stupid www) . I need to be able to access some data source that would be available everywhere.

Now I'm stuck - any ideas?

Answer 1

You can not.

For security reasons the browser only grants access to data stored with localStorage within the same domain. This is due to the fact, that on some systems different subdomains belong to different people / websites.

See for example: http://msdn.microsoft.com/en-us/library/cc197062(VS.85).aspx

Each domain and subdomain has its own separate local storage area. Domains can access the storage areas of subdomains, and subdomains can access the storage areas of parent domains. For example, localStorage['example.com'] is accessible to example.com and any of its subdomains. The subdomain localStorage['www.example.com'] is accessible to example.com, but not to other subdomains, such as mail.example.com.

Answer 2

...Why not use GM_setValue and GM_getValue?

EDIT: I did a little digging. Look what I found!

http://www.opera.com/docs/userjs/specs/#scriptstorage

It claims to work the same as localStorage, but it's scoped per-script, rather than per-website. Should work perfect for your use case.