InterPlanetary File System is a protocol and network designed to create a content-addressable, peer-to-peer method of storing and sharing hypermedia in a distributed file system. IPFS was initially designed by Juan Benet, and is now an open-source project developed with help from the community.
As mentioned in this earlier p2p file seeding post, IPFS would make an amazing external storage option for Nextcloud! See the Nextcloud github feature issue here, or check out the discussion on the new IPFS Discourse Forum. Also, IPFS has developed a javascript implementation.