Well this is meant to be a bad example, really all the babel stuff would be dev dependencies and ideally you'd have some watch task to compile and auto-reload.

Well this is meant to be a bad example, really all the babel stuff would be dev dependencies and ideally you'd have some watch task to compile and auto-reload. In production you'd only have a bundled/minified version transpiled JS so there's no need for a runtime. Ultimately with web assembly this gets even better.