[dspillett]

It is a bit of a "would you really do that in production?" type hack, but there is a pure JS compile of SQLite3 that you could use: https://github.com/kripken/sql.js/

Possible problems:

* Nearly half an MB of library to add to your project which might be a concern on mobile (~2.1MB uncompressed.

* It handles the whole DB in memory rather than trying to use any sort of local storage as a block store, which pumps up memory use (again, mobile user may particularly find this an issue) and to persist data you have to pickle the whole DB as a single array (which could be a significant performance issue if the data changes regularly and is not very small) and reload it upon new visit.

* Concurrency between multiple tabs/windows is going to be an issue for the same reason.