Thank you for pointing this out, I have only been running it as a Chrome extensions or with Node.js.
Not with github.io, I will see if I can make it work this way.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
opened https://floriandh.github.io/EspruinoWebIDE/ in Chrome
see screenshot https://ibb.co/7V5zK3m the error marked happens on each click and dialog does not close. Also there are other errors on load, maybe related.