I’m curious if there is a library or a project out there to provide a generic interface to IndexedDB or to WebSQL, depending on user’s browser’s support. If they’re using Chrome/Safari, use WebSQL, if they’re using Firefox or Internet Explorer, use IndexedDB.
The poster of this question appears to have homegrown a solution, but did not provide any source code.
You might want to go with Lawnchair, which is quite well known, as mentioned by Guido Tapia in the question that you link to.
Either that, or use his picnet.data.DataManager solution.
Also take a look at persistence.js.