fetch is now available as a polyfill or a self-contained library

[steveluscher]

This refactor permits usage of whatwg-fetch as:

• a polyfill that modifies self

  require('whatwg-fetch');

• or as a self-contained module that doesn't

  var fetch = require('whatwg-fetch/library');

Should you use the second form in a project whose code is sometimes executed on the server and sometimes on the client (as is the case with certain classes of apps that do server rendering, or are tested in headless environments), this has the nice side effect of not throwing an exception on import just because self is undefined.

This is similar to the approach taken by core-js.

[mislav]

Sorry, we're not fans. #184 (comment) #31 (comment)

If we accept this pull request, we can't use fetch on GitHub.com anymore, where we don't use any JS module loader. It would be pretty hard to convince us to make a change that prevents us from using our own library in our own product.

[steveluscher]

Thanks for taking a look!

I think you could continue to use it on GitHub, though. This PR builds a ./fetch.js that works just like your old one – with no module loader needed. It's only the additional (and optional) ./library/index.js version that follows the CommonJS pattern.

[mislav]

This PR builds a ./fetch.js that works just like your old one – with no module loader needed.

The creation of ./fetch.js seems to require an extra build step with webpack. That adds complexity to our assets setup. Right now we simply fetch each JS library we use with Bower and load it directly into the site, no post-processing or intermediate build steps needed.

Your "compiled" version of fetch.js is also 0.5 kB larger than ours after minification. Not a huge deal, but considering that the whole library is just over 5k, a 10% size increase is one more reason against our adoption of that approach.

Thanks for taking the time to break down our polyfill into modules, though. It's a good example of how it could be done if a library wanted to take that approach. We feel that our polyfill is still simple enough that it can stay in a single file.