It was working a couple of months ago. When I try it out now, Dart seems to complain that Chrome renamed the XR object so that it's just a generic object with the same API and not an actual instance of the XR class, and that seems to be causing the Dart type checking to go into fits. There's probably a quick fix, but I would have to relearn Dart and its underdocumented JavaScript bindings again to make the fix. Unfortunately, I don't really have the time to look at it at the moment.
Viewing post in Skip Rope VR (WebXR) jam comments
I did end up fixing it in the end. Since WebXR doesn't work on itch.io anyway, I only updated the version on my website with this fixed version. Since this is just a gamejam game that I was using to learn Dart, webxr, and doing 3d stuff in JavaScript, the "game" doesn't really do much. It's just a spinning rope that you can try jumping over if you want. It doesn't feel quite right though. I think the player might need some sort of "body" in VR so that it feels more like they're really jumping.