Switch from Typescript namespaces to ES6 modules

[adamhaile]

NOT READY FOR MERGE

This PR switches kiwi.js from the older Typescript namespace syntax to standard ES6 module syntax (import/export).

Advantages of ES6 modules include:

• it's a standard, so more future proof
• can now also export kiwi.js as ES6 modules, enabling ES6-aware bundlers to do things like tree-shaking

Rollup is added to combine kiwi.js's ES6 modules into a single UMD module.

Current status is that it builds and passes all tests. Minified and JSDoc assets haven't been updated yet.

To run the new build, run npm run rollup. Take a look and see if you're comfortable with the general approach. If you are, I'll replace the grunt build with the rollup one as well as add the steps to build kiwi.min.js and Kiwi.md.

[codecov-io]

Codecov Report

Merging #7 into master will increase coverage by 2.44%. The diff coverage is 86.36%.

@@            Coverage Diff             @@
##           master       #7      +/-   ##
==========================================
+ Coverage   71.22%   73.66%   +2.44%     
==========================================
  Files           1        1              
  Lines         827      638     -189     
  Branches      124       94      -30     
==========================================
- Hits          589      470     -119     
+ Misses        238      168      -70

Impacted Files	Coverage Δ
lib/kiwi.js	73.66% <86.36%> (+2.44%)	:arrow_up:

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[adamhaile]

Docs and minified build now work.

Some notes:

• ES6 modules can't be simply concated like AMD ones, and as you know Typescript's UMD format only supports AMD and CommonJS, not browser globals, so I brought in rollup to do both those tasks. Rollup also has the nice feature that it flattens the internal modules into a single namespace, removing internal module boilerplate and making for a smaller package. It's arguably the best bundler for libraries right now.

Alternative: if you're uncomfortable/unfamiliar with rollup I could change the typescript config to output AMD modules, which can then follow your old strategy of concat and wrap with a UMD loader.

• With these changes, the string replacements you had devised to get jsdoc2md to work no longer matched the output. Instead of updating them, I did some experimentation and figured out that jsdoc2md could handle a full es6 compilation just fine -- one where we leave class statements as they are rather than having typescript down-compile them to es5 function statements. Kiwi.md is even arguably improved, in that class descriptions are now under the classes themselves rather than their constructors. IE 10 and 11 still don't support class statements, so using this output alone would be a breaking change. Therefore, the build does a separate es6 compilation in tmp, then runs jsdoc2md on that.

• With the string replacements and concat+wrap removed, there wasn't much left for grunt to do, so I removed it and replaced its tasks with direct calls to the utilities in package.json.

This ended up being a bigger set of changes than I initially anticipated. Very little code is changed in the core lib, but the build is different. If this is more than you're comfortable with, we can discuss intermediate strategies. Or you can just ditch the PR. It's your library :).

To disclose my interest here, I'm evaluating kiwi.js for use in my startup's product. I was attracted to it for speed, clean design and indicators of code quality (tests, docs, activity, etc). We definitely need Typescript typing support, which is why the existing package doesn't work for us (see issue #6). We prefer a modern build, as if we go with kiwi.js, I suspect we'll need to get to know its internals. We can run our own fork but if our changes are consistent with your direction for the library it makes sense for us to contribute upstream, as always with open source.

[IjzerenHein]

Hey man, this is great work, I will try to review and merge this shortly! Cheers, Hein

[IjzerenHein]

Hi, I've merged all your code, looks really good! I just removed the es folder from the git repo. It's still published in the NPM package, but I always want to prevent auto-generated code to be contained in the git repo. Thanks so much for this PR, this paves the way for the future. Cheers dude!