javascript library for client side storage with server side sync [closed]
Just stumbled across this question; for posterity, CouchDB and CouchBase are designed for this:
The JavaScript client:
And CouchBase:
Finally, CouchBase Lite/Mobile:
https://www.couchbase.com/products/lite
The latter gets you native CouchDB/CouchBase synchronization.
In all cases you just access the local database and it can synchronize if and when you connect to the internet.
Store.js deal with the client-side storage very well. Note that it supports IE6+ along with other browsers. For the server-side storage you might as well make your own script for that as it should not be difficult.
Since this question was asked, there's been a lot of work done on local storage and client side databases.
There's a great overview of local storage options at Dive Into HTML5.
There are also several cross-platform JavaScript storage libraries available, including Lawnchair and persistence.js.