Module System and Angular Style Dependency Injection 63 lines of Javascript.

module.js

(function(window) {

  // global module list
  var modules = {};

  // require a module
  window.require = function(name) {
    return modules[name];
  };

  // create a module getter on window
  window.__defineSetter__('module', function(module) {
    var deps = [];

    // Check that a named function has been passed
    if(!module.name) {
      throw new Error('Modules need names!');
    }

    // Make sure it's not overriding a current module
    if(module.name in modules) {
      throw new Error('Module already exists');
    } else {
      // check dependencies
      deps = getArgNames(module);

      // store the result of calling the module
      // with its dependencies injected
      // + give it a new context for 'this'
      // passing lambda to be later resolved,
      // in order to avoid cyclic dependency
      // errors.
      modules[module.name] = module.apply({}, deps.map(resolve));
    }
  });

  // turn a name into a module
  function resolve(name) {
    if(name in modules) {
      return modules[name];
    } else {
      throw new Error('Could not resolve dependency: ' + name);
    }
  }

  // returns itself for filter functions
  function identity(value) {
    return value;
  }

  // returns an array of argument names
  function getArgNames(fn) {
    var str, exp;

    str = fn.toString();
    exp = /\(([a-zA-Z0-9_$, ]*)\)/;
    return exp.exec(str)[1]
      .replace(' ', '')
      .split(',')
      .filter(identity);
  }

})(window || global);