Disclosure: I'm the author of a competing JavaScript database (http://gunDB.io/).
Unfortunately concurrency is typically the
last thing that people think about. Concurrency is the first thing we deal with in our database, because you are right, without it data gets corrupted.
Yes, although right now I am doing that with websockets which is silly for local stuff. We are wanting to add WebRTC as well, but we could also add what you are talking about - make an issue for it on the github (although it will probably be low priority)
Check out intercom on github for inter-tab communication. I use it in we apps for many different things. Including log-back-in. One tab gets a session timeout and tells them all to go black asking for a password. Enter it in one tab and they all unlock.
Unfortunately concurrency is typically the last thing that people think about. Concurrency is the first thing we deal with in our database, because you are right, without it data gets corrupted.