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