[whatwg] sessionStorage and the Storage event

Honza Bambas honzab at allpeers.com
Tue Oct 27 09:52:59 PDT 2009

Ian Hickson wrote:
> On Tue, 27 Oct 2009, Honza Bambas wrote:
>> The spec says:
>> "When the |setItem()
>> <http://dev.w3.org/html5/webstorage/#dom-storage-setitem>|, |removeItem()
>> <http://dev.w3.org/html5/webstorage/#dom-storage-removeitem>|, and |clear()
>> <http://dev.w3.org/html5/webstorage/#dom-storage-clear>| methods are called on
>> a |Storage <http://dev.w3.org/html5/webstorage/#storage-0>| object x that is
>> associated with a session storage area, if the methods did something, then in
>> every |HTMLDocument| object whose |Window| object's |sessionStorage
>> <http://dev.w3.org/html5/webstorage/#dom-sessionstorage>| attribute's |Storage
>> <http://dev.w3.org/html5/webstorage/#storage-0>| object is associated with the
>> same storage area, other than x, a |storage
>> <http://dev.w3.org/html5/webstorage/#event-storage>| event must be fired, as
>> described below <http://dev.w3.org/html5/webstorage/#event-storage>."
>> [http://dev.w3.org/html5/webstorage/#dom-sessionstorage]
>> The same applies to localStorage.
>> Maybe I read something wrong, but as a sessionStorage object is always 
>> unique to its document (it is cloned when a new document with the same 
>> origin is created and then independent from the original document's 
>> object) it, in my opinion, doesn't make sense to send the event to any 
>> other document then the one its storage has been changed. On the other 
>> hand, it makes sense to me to not fire the event in the same document 
>> where the storage has been changed (as for localStorage), then, I'd say 
>> there should be no event for sessionStorage at all. I simply don't a 
>> case when two or more documents would share a single sessionStorage 
>> object.
>> Thanks for clearing this.
> You can have multiple (active) documents sharing the same sessionHistory 
> using nested browsing contexts, for example in <iframe>, <object>, and 
> <frameset>/<frame>.
s/sessionHistory/sessionStorage/ ?

Ah, true. sessionStorage object is shared within the toplevel browsing 
context for all nested documents with the same origin. Then it makes 
sense to send the message to all those documents.

Thanks for clarifying.

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