PouchDB - The JavaScript database that Syncs

PouchDB was written to help web developers build applications that work as well offline as well as they do online, applications save data locally so the user can use all the features of an app even while offline and synchronise the data between clients so they have up to date data wherever they go.

PouchDB Example

PouchDB is Open Source, written in Javascript and inspired by Apache CouchDB, it is designed to be lightweight and easily embeddable.

Cross Browser 
PouchDB uses various backends so it can work across various browsers and in Node.js. It uses IndexedDB in Firefox and Chrome, WebSQL in Safari and Opera and LevelDB in Node.js.
Currently tested in:

• Firefox 12+
• Chrome 19+
• Opera 12+
• Safari 5+
• Node.js 0.10+
• Apache Cordova
• Internet Explorer 10+

If your application requires support for Internet Explorer below version 10, it is possible to use an online CouchDB as a fallback, however it will not work offline.

PouchDB Project Page

NeDB - Embedded datastore for node.js

NeDB

NeDB is embedded persistent database for Node.js, written in Javascript, with no dependency (except npm modules of course). You can think of it as a SQLite for Node.js projects, which can be used with a simplerequire statement. The API is a subset of MongoDB's. You can use it as a persistent or an in-memory only datastore.

NeDB is not intended to be a replacement of large-scale databases such as MongoDB! Its goal is to provide you with a clean and easy way to query data and persist it to disk, for web applications that do not need lots of concurrent connections, for example a continuous integration and deployment server and desktop applications built with Node Webkit.

NeDB | GitHub