John Resig 写了一个漂亮的 Class 函数，很时髦。我试图弄清楚发生了什么，并且除了一行之外几乎所有的东西都弄清楚了：

fnTest = /xyz/.test(function () {xyz;}) ? /\b_super\b/ : /.*/;

有几件事立即浮现在脑海中，首先xyz是永远不会初始化为变量；那么为什么这样做呢？其次，为什么要/xyz/针对不返回任何内容的内容进行测试（无返回语句）。除非有一些我不知道的 javascript 的漂亮属性（这是可能的，我认为自己很擅长 JS 并且可以解释我遇到的大多数代码，但是，这并不意味着我在同一个山上.约翰雷西格称之为家的珠穆朗玛峰大小的山）。

对于那些好奇的人，这里是来自 john resigs 站点John Resig Simple Javascript Inheritance的完整未编辑代码：

(function () {
  var initializing = false, fnTest = /xyz/.test(function(){xyz;}) ? /\b_super\b/ : /.*/;

  // The base Class implementation (does nothing)
  this.Class = function(){};

  // Create a new Class that inherits from this class
  Class.extend = function(prop) {
    var _super = this.prototype;

    // Instantiate a base class (but only create the instance,
    // don't run the init constructor)
    initializing = true;
    var prototype = new this();
    initializing = false;

    // Copy the properties over onto the new prototype
    for (var name in prop) {
      // Check if we're overwriting an existing function
      prototype[name] = typeof prop[name] == "function" &&
        typeof _super[name] == "function" && fnTest.test(prop[name]) ?
        (function(name, fn){
          return function() {
            var tmp = this._super;

            // Add a new ._super() method that is the same method
            // but on the super-class
            this._super = _super[name];

            // The method only need to be bound temporarily, so we
            // remove it when we're done executing
            var ret = fn.apply(this, arguments);       
            this._super = tmp;

            return ret;
          };
        })(name, prop[name]) :
        prop[name];
    }

    // The dummy class constructor
    function Class() {
      // All construction is actually done in the init method
      if ( !initializing && this.init )
        this.init.apply(this, arguments);
    }

    // Populate our constructed prototype object
    Class.prototype = prototype;

    // Enforce the constructor to be what we expect
    Class.constructor = Class;

    // And make this class extendable
    Class.extend = arguments.callee;

    return Class;
  };

})();