[xvolter]

I do not think it is.

Blockchains are meant as a data store. Archival, verifiable. But not easily searchable. There is no design on blockchain for advanced query languages/logic.

It seems like the OP is going after something like blockchain that adds querying. But I don't think blockchain syncing is designed well enough for client-side use, and the OP seems to want to use this database client-side in JavaScript. I think it would be possible to implement blockchain syncing with WebRTC, but WebRTC has some security risks for users (IP leakage mostly) so I am not sure I would start off with that as a primary communication channel.