Rollup
A module bundler for JavaScript
...ES modules let you freely and seamlessly combine the most useful individual functions from your favorite libraries. This will eventually be possible natively everywhere, but Rollup lets you do it today. Rollup can be used either through a command line interface with an optional configuration file, or else through its JavaScript API. Rollup allows you to write your code using the new module system, and will then compile it back down to existing supported formats such as CommonJS modules, AMD modules, and IIFE-style scripts. This means that you get to write future-proof code.