I'd definitely be up for this. Count me in
I've already implemented those dijkstra maps in my javascript RL prototype, and was amazed at how they seemed to imbue the NPCs with a clear sense of purpose. Found it very slow to update the map, though, but I guess that's the fault of me having an incredibly inefficient map structure in my prototype and iterating every tile.
I'm not terribly familiar with JS, so I'm not sure it this's even possible, but you might want to try multi-threading your calculations. I assume you've got more than one dijkstra map, so you could assign 1 thread per map. Since each thread is accessing shared data in a read-only fashion and writing only to its own separate output, locking/etc. shouldn't be a problem.
But again, I'm not sure if/how you can do multi-threading in javascript.
JS isn't capable of true multi-threading, unfortunately. It's far too high-level to give the developer any meaningful agency when it comes to memory management, process control, or other things of that nature.
It does, however, have event handling, so it is possible in theory to simulate multithreading by creating event callbacks which would perform particular calculations asynchronously, which would help stop intensive processes from causing the browser to become unresponsive.
My prototype is a very nastily written thing that is used more as a testbed for quick prototyping of concepts (my most recent one is an attempt at simulating atmospheric pressure to see if an idea of mine set in space would be feasible) before I decide that either the concept doesn't work well, or, if I like it, I then refactor it for inclusion into the more advanced engine that handles things like map subdivision far more elegantly.