nengi

I use phaser on client side, then matter.js for physics + nengi.js for networking (https://github.com/timetocode/nengi). I only have experience with 2d (so it might not be useful to you, but perhaps will others), where typically it's a worse experience for the player to have CSP (client side prediction) at-least in a fast paced game, as for example a player behind a wall can more clearly see something missed them, yet they still got hit. The way I do things (and I've seen is common across other "io" games), is "CSP" only for particular actions (such as your own rotation, or swinging your own weapon), but otherwise just let the client move in step with the server in terms of any physics entities etc.

On a lower level, I have been using Colyseus (https://github.com/colyseus/colyseus) which is, in the words of the author: "[...] an Authoritative Multiplayer Framework for Node.js, with clients available for the Web, Unity3d, Defold, Haxe, and Cocos2d-X.". I have been using it on multiple projects as a state synchronisation library for my browser-based games. It takes cares of all the data synching aspecta among all players in a "room". The community is very active and you will get a lot of help to begin with and scale your creations. Of course, a lot will have to be done by you for anything like client-side prediction, server reconciliation, lag compensation, entity interpolation, but knowing that the state manages itself is already a huge relief if you are unfamiliar with these concepts. Another project which already includes many of th