So when ActionScript is compiled to JS, do they mean it's actually pure JS, or is this getting converted into ASM.JS? Historically, a big appeal of Flash vs. JS has been performance - ActionScript is an ugly language, but it's statically typed. And JS/canvas/whatever historically haven't been too efficient at moving vectored objects around the screen.

Then again, a the factor in Flash's favour isn't the run-time, its' the development workflow.