[whatwg] Structured clone algorithm on LocalStorage

Jonas Sicking jonas at sicking.cc
Wed Sep 23 15:15:40 PDT 2009

On Wed, Sep 23, 2009 at 2:53 PM, Brett Cannon <brett at python.org> wrote:
> On Wed, Sep 23, 2009 at 13:35, Jeremy Orlow <jorlow at chromium.org> wrote:
>> What are the use cases for wanting to store data beyond strings (and what
>> can be serialized into strings) in LocalStorage?  I can't think of any that
>> outweigh the negatives:
>> 1)  From previous threads, I think it's fair to say that we can all agreed
>> that LocalStorage is a regrettable API (mainly due to its synchronous
>> nature).  If so, it seems that making it more powerful and thus more
>> attractive to developers is just asking for trouble.  After all, the more
>> people use it, the more lock contention there'll be, and the more browser UI
>> jank users will be sure to experience.  This will also be worse because
>> it'll be easier for developers to store large objects in LoaclStorage.
>> 2)  As far as I can tell, there's no where else in the spec where you have
>> to serialize structured clone(able) data to disk.  Given that LocalStorage
>> is supposed to throw an exception if any ImageData is contained and since
>> File and FileData objects are legal, it seems as though making LocalStorage
>> handle structured clone data has a fairly high cost to implementors.  Not to
>> mention that disallowing ImageData in only this one case is not intuitive.
>> I think allowing structured clone(able) data in LocalStorage is a big
>> mistake.  Enough so that, if SessionStorage and LocalStorage can't diverge
>> on this issue, it'd be worth taking the power away from SessionStorage.
>> J
> Speaking from experience, I have been using localStorage in my PhD
> thesis work w/o any real need for structured clones (I would have used
> Web Database but it isn't widely used yet and I was not sure if it was
> going to make the cut in the end). All it took to come close to
> simulating structured clones now was to develop my own compatibility
> wrapper for localStorage (http://realstorage.googlecode.com for those
> who care) and add setJSONObject() and getJSONObject() methods on the
> wrapper. Works w/o issue.

Actually, this seems like a prime reason *to* add structured storage
support. Obviously string data wasn't enough for you so you had to
write extra code in order to work around that. If structured clones
had been natively supported you both would have had to write less
code, and the resulting algorithms would have been faster. Faster
since the browser can serialize/parser to/from a binary internal
format faster than to/from JSON through the JSON serializer/parser.

/ Jonas

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