[notduncansmith]

You may want to check out the CouchDB project, they recently added a Mongo-like query interface. Also check out PouchDB, the JS version of Couch which can use (among other browser storage options) IndexedDB, offers a Mongo-like query interface, and syncs with Couch. There may be some good ideas in there that you can use for your own project.

[erikolson186]

The functionality and behavior of ZangoDB was tailored specifically for porting a rather complex Mongo-based application to the browser. Syncing was not one of the requirements. However, I am currently working towards adding syncing support, and I am investigating developers' requirements. I will look into how PouchDB handles this. Thank you!