Converted CoffeeScript and CJSX to ES6 and JSX

[gesposito]

Notes about conversion

Automation

I used
https://github.com/js2coffee/js2coffee
for CoffeeScript files and

https://github.com/jsdf/coffee-react
for CJSX ones.

Conversion

require are translated to imports, with optional destructuring assignment:
import { prune, include as includes } from 'underscore.string';

CSS are imported thanks to webpack:
import '../css/styles.css';

@props are converted to this.props thanks to React.autoBind.

JSX tags stay the same, style properties need commas.

Spread ... operators stay the same.

Multiline strings and template strings need backticks ``` instead of single/double quotes.
String substitution in template strings need the ${var} syntax instead of `#{var}`.

var should probably be replaced by either let or const.

ES6 Classes

I personally prefer ES6 Classes over React.createClasses but that would require some more changes in the gatsby codebase and they would be a bit opinionated right now.

[KyleAMathews]

Nice!

I tested this (gatsby new blog https://github.com/gesposito/gatsby-starter-blog) and once I commited this gatsbyjs/gatsby@563604d everything worked perfectly.

Thanks!

[Vadorequest]

@gesposito Hi. I'm just wondering why you changed your code from cjsx to jsx+es6. I'm about to start a cjsx project and I'm wondering if you have met any downside with cjsx.

Thanks.

[gesposito]

@Vadorequest Gatsby and its starter projects were originally developed in CoffeeScript but I suggested @KyleAMathews to move the codebase to ES6 for contributions and adoption
gatsbyjs/gatsby#1 (comment)
mainly because the React ecosystem is mostly involved into ES6.

There were no problems with CoffeeScript or cjsx (at least that I knew about), but I understand that ES6 is giving JS most of what CoffeeScript was there for.

Not sure if it helped or it was just great timing, but Gatsby exploded in adoption since then.

[KyleAMathews]

@Vadorequest I still use Coffeescript/CJSX on my sites. The three big advantages of ES6 are better tooling, larger community, and greater velocity. Coffeescript used to be far ahead of ES5 in ease-of-use but ES6 has adopted many of its innovations now so it's not as easy to justify.

[Vadorequest]

Thanks to both of you for inputs! :)