I am also working on JS client-server multiplayer implementations, and I've gone with WebRTC for the transport and a state-based communication (instead of event

I am also working on JS client-server multiplayer implementations, and I've gone with WebRTC for the transport and a state-based communication (instead of events). The primary reason is to avoid desyncs, which is in my opinion impossible to avoid with JS because of the different JS engines and platforms that the game will run on. If you're expecting determinism when playing across mobile ARM, desktop x86, desktop ARM, and any combination of these, then the only way to achieve this is to use fixed point math and reimplement the behavior of JS primitives such as arrays and hash tables. It might be worth it for you and the game you're making, but for fast action games this is not needed, and just sending state to the players should work well.