Hi,
I worked a bit on a Javascript runtime, this is available on my github: https://github.com/tleunen/spine-js
I currently don't have any example to show you, but if you download the runtime, there is an example in the test folder.
The runtime is highly based on the C++ runtime (btw, I don't see this runtime anymore on the esotericsoftware github, is it normal?), so if you take a look at the files, you should not be lost!
I'll try to keep it up to date with latest changes in the others runtimes, but I still have a few improvements to make, like adding the AnimationState and the atlasing, fixing the animation scaling (doesn't seem to work properly), and cleaning the unused stuff.
Thanks 😉