I previously tried to create a live JS object environment, however I used the Self prototype model rather than the Smalltalk model - https://rameshvarun.github.io/protoworld/. Version control is handled through an implementation of Self's transporter which serializes live object graphs into diffable code. The biggest issue is that there is so much UI work required just to match what you would get with a standard text editor and terminal.

Video Demo: https://youtu.be/pmU1sbgxRng Source: https://github.com/rameshvarun/protoworld/