John Resig编写了一个很棒的类函数swanky。我正在尝试弄清楚发生了什么，并且几乎已经弄清楚所有东西，除了一行：
fnTest = /xyz/.test(function () {xyz;}) ? /\b_super\b/ : /.*/;
一些事情立即浮现在脑海中。首先，
xyz从未初始化为变量; 那么为什么这个可以工作呢？其次，为什么要将/xyz/与未返回任何内容的东西进行测试（没有返回语句）。除非有我不知道的JavaScript的巧妙属性（这是可能的，我自认为在JS方面相当擅长，并且可以解释我遇到的大多数代码，但这并不意味着我和John Resig生活在同一个珠穆朗玛峰大小的山上）。
对于那些好奇的人，这是来自john resigs网站的完整未编辑代码John Resig Simple Javascript Inheritance：
(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;
};
})();