Node.js中对通用模块的封装方法

和Underscore.js 类似的Lo-Dash，也是使用了类似的方案，只是兼容了AMD模块载入的兼容：
 
;(function() {
  /** Used as a safe reference for `undefined` in pre ES5 environments */
  var undefined;
    /** Used to determine if values are of the language type Object */
      var objectTypes = {
        ‘boolean’: false,
        ‘function’: true,
        ‘object’: true,
        ‘number’: false,
        ‘string’: false,
        ‘undefined’: false
      };
  /** Used as a reference to the global object */
  var root = (objectTypes[typeof window] && window) || this;
  /** Detect free variable `exports` */
  var freeExports = objectTypes[typeof exports] && exports && !exports.nodeType && exports;
  /** Detect free variable `module` */
  var freeModule = objectTypes[typeof module] && module && !module.nodeType && module;
  /** Detect the popular CommonJS extension `module.exports` */
  var moduleExports = freeModule && freeModule.exports === freeExports && freeExports;
/*————————————————————————–*/
  // expose Lo-Dash
  var _ = runInContext();
  // some AMD build optimizers, like r.js, check for condition patterns like the following:
  if (typeof define == ‘function’ && typeof define.amd == ‘object’ && define.amd) {
    // Expose Lo-Dash to the global object even when an AMD loader is present in
    // case Lo-Dash was injected by a third-party script and not intended to be
    // loaded as a module. The global assignment can be reverted in the Lo-Dash
    // module by its `noConflict()` method.
    root._ = _;
    // define as an anonymous module so, through path mapping, it can be
    // referenced as the “underscore” module
    define(function() {
      return _;
    });
  }
  // check for `exports` after `define` in case a build optimizer adds an `exports` object
  else if (freeExports && freeModule) {
    // in Node.js or RingoJS
    if (moduleExports) {
      (freeModule.exports = _)._ = _;
    }
    // in Narwhal or Rhino -require