CouchDB Alternatives for JavaScript

TaffyDB is a free and open source, Pure-JavaScript database abstraction that stores data in JSON format. TaffyDB provides INSERT, DELETE, GET (SELECT)  and JOIN methods to execure the data similar to that of traditional relational SQL databases. TaffyDB allows you to quickly setup an in-memory database that can be used in the same fashion as an SQLite database would, without configuration and a database server running.

RethinkDB is a scalable, open-source database designed for real-time applications. When your app polls your database for data, it becomes slow, unscalable, and cumbersome to maintain. RethinkDB solves this by providing a new database access model, where developers can instruct the database to continuously push updated query results to their applications, without polling.

PouchDB is a free and open-source JavaScript database inspired by Apache CouchDB. The database is designed from the ground-up to run well within modern web browsers. With PouchDB you can create web applications that works as well offline as they do online. PouchDB achives this by storing data locally, then synchronize it with CouchDB and compatible servers when the user get internet access once again. This is especially useful for applications facing countries and regions with lower quality internet connections or unstable infrastructure.