I used Babylon.js for the 3D game/controls, and I imported free 3D assets from various asset stores for the content. The backend was a simple socket server written in Node.js with socket.io connected to the web frontend via JS using the standard WebSockets API. I got realtime character movement, turning, & jumping implemented pretty quickly. Content became a bottleneck so I stopped developing, but I hope to finish it up sometime in the near future.
Good luck!