Is there a performant JSON based DB with a client side implementation?
I found this question about SQL-like query libraries. What I am looking for is a library that allows queries on JSON objects, embedded in a client-side application (browser), as well as from a remote high performance dedicated database.
You could try couchbase lite (client side) that syncs with couchbase server.
It is a document based nosql database, querying isn't as rich as SQL but you have the ability to create additional indices on which to query your data by using couchbase views (map reduce jobs). These work both on the client and server, it also supports syncing between the device and server.
For the sake of completeness I'll throw out PouchDB and CouchDB.
I was searching for the same thing and after much searching suddenly came across NeDB, which now has a browser implementation.
Unlike PouchDB it has a Mongo-like query API.