Hey, Framers. Lesson learned..
I wanted to use an external JS library and tried to use DOM element (Layer._element) to initiate the module, but it wasn't working. After many hours of trial and error, decided to just create dummy DOM elements outside of Framer layers and let them handles JS events. Here is the demo.
BUT! at last, I realized that I can just add a dummy event handler, which do nothing, on Layer like "test.on Events.Click, ->", then the event handler added by external JS library just started to work.. (Try rotate the square)
I just lost my half day. Sharing a tip for you.