Module loader in CommonJS style

annotated.js

(
  function (
      mods,                   // module storage
      vals                    // module values storage
    ) {
    return function req (     // return a "require" function
      name,                   // module name OR callback to run
      def                     // module definition
    ) {
      return name.call ?      // if first argument is callback
          name(req)           // run it with "require" as first argument
        : def ?               // if we define a module 
          (mods[name] = def)  // save it to storage
        : name in vals        // if we have value saved
          ? vals[name]        // return it 
          : (vals[name] = (   // else save the value
            mods[name](       // of the definition called
              req,            // with "require" as first argument,
              def = {         // "module" as second argument
                exports: {}
              }, def.exports  // and "exports" as third argument
            ) || def.exports  // or use module.exports if no value returned
          ))
    }
  }
)({}, {})

index.js

(function(d,c){return function e(a,b){return a.call?a(e):b?d[a]=b:a in c?c[a]:c[a]=d[a](e,b={exports:{}},b.exports)||b.exports}})({},{})

LICENSE.txt

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
                    Version 2, December 2004

 Copyright (C) 2011 YOUR_NAME_HERE <YOUR_URL_HERE>

 Everyone is permitted to copy and distribute verbatim or modified
 copies of this license document, and changing it is allowed as long
 as the name is changed.

            DO WHAT THE FUCK YOU WANT TO PUBLIC LICENSE
   TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

  0. You just DO WHAT THE FUCK YOU WANT TO.

package.json

{
  "name": "tinyCommonJSishModuleLoader",
  "description": "Module loader in CommonJS style",
  "keywords": [
    "module",
    "loader"
  ]
}

test.html

<script>
  var module = (function(d,c){return function e(a,b){return a.call?a(e):b?d[a]=b:a in c?c[a]:c[a]=d[a](e,b={exports:{}},b.exports)||b.exports}})({},{})
  var counter = 1

  // simple module definition
  module('a', function (require) {
    return counter++
  })

  // CommonJS-ish style
  module('b', function (require, module, exports) {
    module.exports = counter++
  })

  // entry point
  module(function (require) {
    console.assert(require('a') === 1)
    console.assert(require('b') === 2)
    console.assert(require('a') === 1) // values are cached
    console.log('Module loaded!')
  })
</script>

<script>
  // BONUS: loading modules from network  
  var loadModule = function (name, base, req) {
    req = new XMLHttpRequest()
    req.open('GET', base + name + '.js', false)
    req.send()
    module(name, Function('require', 'module', 'exports', req.responseText))
  }
  var base = '/scripts/'
  loadModule('example', base) // loads /scripts/example.js
  console.log(module('example'))
</script>