Explore babel-preset-env

[tizmagik]

With #255 we now have babel-polyfill in place both on the client and server for necessary ES6+ support. In the case of the client, relatively modern browsers don't need the entire polyfill, and for the server since node 6 is already a pre-req for kyt, most of the polyfill is also unnecessary there.

Although it's arguably still early for babel-preset-env, I think it might be good to experiment with it and see if we can use it to polyfill only what's necessary for newer browsers in the client bundle and node 6+ in the server bundle.

[delambo]

I can't get a good read on babel-preset-env. Does it actually include polyfills or is it for transformation only? If it's the latter, I don't think it would be a replacement for babel-polyfill.

[tizmagik]

No, unfortunately it's not a replacement for babel-polyfill, it just results in less code being transpiled and, presumably, a smaller overall bundle size.

However, something to only polyfill what's needed seems like it's in the cards for babel-preset-env, see this issue: babel/babel-preset-env#20

With that being said, on the server-side we might be able to get away with only polyfilling what's missing (e.g. generator functions, etc) and leave off the rest since node 6 has pretty decent ES6 coverage and it's a more predictable environment. We wouldn't be able to leave off the polyfill for the browser, however.

[hzoo]

Babel itself only transforms syntax so the preset just determines the least common denominator of plugins to run on the browsers/environments you specify in the options. Instead of changing your set of plugins yourself (turning off plugins over time) it should calculate that for you.

[hzoo]

I'm working on the polyfill part in babel/babel-preset-env#56