[hawski]

I am not JS dev, but... At this point there should be tree shaking / dead code removal for JS widely deployed. Why it is not? I know that dynamic nature of JS causes some of it, but most code out there is not that dynamic. How good is Google's Closure compiler?

[lloyd-christmas]

rollupjs.org as well as webpack2 are doing this. As you said, the dynamic nature will prevent this from being native. Using a build tool isn't terrible though.