象使用java类一样使用javscript类，javascript 类机制实现源码

1 象使用java类一样使用javscript类，javascript 类机制实现源码
    习惯了使用java， 转入到javascript后， 一直苦恼为什么不能象java那样建立类及其对象呢。
尝试了很多方式， 最近在网上看到一段代码， 才发现原来在js中可以如此简单高效的实行类机制。
也打消了我对javascript类机制会特别消耗性能的顾虑，让我放心的使用javascript类机制。

代码比较短，只用了js的基本特性。参考价值比较高，在这里show一下代码。

实现类机制代码如下：

javascript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.prototype.constructor = Class;

    // And make this class extendable
    Class.extend = arguments.callee;
  
    return Class;
  };
})();

测试代码如下：
javascript代码
var Person = Class.extend({
  init: function(isDancing){
    this.dancing = isDancing;
  },
  dance: function(){
    return this.dancing;
  }
});
var Ninja = Person.extend({
  init: function(){
    this._super( false );
  },
  dance: function(){
    // Call the inherited version of dance()
    return this._super();
  },
  swingSword: function(){
    return true;
  }
});

var p = new Person(true);
p.dance(); // => true

var n = new Ninja();
n.dance(); // => false
n.swingSword(); // => true

// Should all be true
p instanceof Person && p instanceof Class &&
n instanceof Ninja && n instanceof Person && n instanceof Class