Refactor to use ES Modules + Rollup (CJS, ESM, UMD) + Babel + ESLint/Prettier

[dmnsgn]

This is a big one: it includes a lot of changes and some stylistic ones so I'd understand if you don't like some of them and you might also not have the time to review it but I figured I tried. Also I have seen you were interested in switching to ES modules (#102) so here it is:

• Refactor to use ES Modules
• Use Rollup to get three bundles CJS, ESM, UMD
• Use Babel and encourage the use of babel-polyfill
• ESLint/Prettier for code consistency
• Remove Grunt in favour of Rollup
• Remove Closure Compiler in favour of Babel
• Use JSDoc to generate a documentation: https://dmnsgn.github.io/fontfaceobserver/

All tests are the same and passing in Node 4 to 8: https://travis-ci.org/dmnsgn/fontfaceobserver

You can see the output bundles keep a small size gzipped:

• https://unpkg.com/fontfaceobserver-es@3.1.1/dist/fontfaceobserver.cjs.js (gzip 1.6 kB)
• https://unpkg.com/fontfaceobserver-es@3.1.1/dist/fontfaceobserver.esm.js (gzip 4.26 kB)
• https://unpkg.com/fontfaceobserver-es@3.1.1/dist/fontfaceobserver.umd.js (gzip 2.22 kB)

I published it on npm to have a play: https://www.npmjs.com/package/fontfaceobserver-es

Thanks

[gmcdev]

Nice freaking work, dude! Saving my life right now, since my project compiles with webpack and rollup. Of course it was freaking out about the commonjs export.

[bennypowers]

It would be wonderful if this was published as es modules.

[dmnsgn]

Updated with latest commits and fixes: https://unpkg.com/fontfaceobserver-es@3.3.1/dist/fontfaceobserver.esm.js

Fixed all the tests

Available to test from at: npm i fontfaceobserver-es

[scsskid]

thanks!

[sandinosaso]

Can I help anyway to make this PR merged? I think this is very important, Currently many projects use webpack or rollup, and having this library not being tree shakable is a big down for those.

In our case, we detected that our bundle size incremented > 40% due to just use this library, and we are investigating to move away from it for this very reason.

[tiye]

Thanks for the package fontfaceobserver-es .

[danimalweb]

Love to see this merged, please?

[rafagsiqueira]

I can also confirm fontfaceobserver-es works when using the following import:
import FontFaceObserver from 'fontfaceobserver-es';