ES2015 Modules

Not yet native available in any environment (include Node v0.5.X).

Rollup

Rollup enables you to use ES6 modules for front end code today.

Essentially, just like Browserify or Webpack, it bundles all your seperate JS modules into a single file. Due to inherent differences between CommonJS and ES6 modules, methods such as Tree-Shaking can greatly reduce the final filesize. Due to the lack of wrapper functions are modules, Rollup bundles are also several orders of magnitude faster during runtime.