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ES6 Module Loading in Node.js

Guiding Principles

The solution must be 100% backward-compatible.
In the far future, developers should be able to write Node programs and libraries without knowledge of the CommonJS module system.
Module resolution rules should be reasonably compatible with the module resolution rules used by browsers.
The ability to import a legacy package is important for adoption.

Design Summary

This article has been given a more permanent home on my blog. Also, since it was first written, the development of the Promises/A+ specification has made the original emphasis on Promises/A seem somewhat outdated.

You're Missing the Point of Promises

Promises are a software abstraction that makes working with asynchronous operations much more pleasant. In the most basic definition, your code will move from continuation-passing style:

getTweetsFor("domenic", function (err, results) {
 // the rest of your code goes here.

	var webpack = require('webpack');
	var MemoryFS = require('memory-fs');
	var SingleEntryDependency = require('webpack/lib/dependencies/SingleEntryDependency');
	var fs = new MemoryFS();

	fs.mkdirpSync('/src');
	fs.writeFileSync('/src/app.js', 'require("./dep.js")', 'utf-8');
	fs.writeFileSync('/src/dep.js', 'module.exports = function(msg){console.log(msg)}', 'utf-8');
	fs.writeFileSync('/src/extra-entry.js', 'require("./dep.js")', 'utf-8');