prototype中继承的有关问题

/*
 * 第一种方法,不使用prototype的继承
 * 这是以前在学习继承时使用的继承方法，
 */
function d(ui){
	if(!ui){
		return;
	}
	this.param1 = document.createElement(ui);
}

function e(ui){
	if(!ui){
		return;
	}
	this.base = d;
	this.base(ui);
	this.param2 = document.createElement(ui);
}
e.prototype = new d();

function f(ui){
	if(!ui){
		
	}
	this.base = e;
	this.base(ui);
}
f.prototype = new e();

var e1 = new e("div");
var e2= new e("div");
var f1 = new f("div");
var f2 = new f("div");
//能够拿到不同的param1对象
alert(e1.param1 ==e2.param1); //返回false
alert(f1.param2 == f2.param2);//返回false

/*
 * 第二种方法,使用prototype继承
 */
 
var a = Class.create();
a.prototype = {
	initialize:function(ui ){
		this.param1 = document.createElement(ui);
	}
}

var b = Class.create();
b.prototype = Object.extend(new a(),{
	initialize:function(ui){
		this.param2 = document.createElement(ui);
	}
})

var c = Class.create();
c.prototype = Object.extend(new b(),{
	initialize:function(param){
	}
})

var b1 = new b("div");
var b2= new b("div");
var c1 = new c("div");
var c2 = new c("div");
//这里本意是每一个对象都能拿到自己的一个param1的属性
//但是这里拿到的是同一个引用
alert(b1.param1 == b2.param1);//return true
alert(c1.param2 == c2.param2);//return true

Object.extend = function(destination, source) {
  for (var property in source) {
    destination[property] = source[property];
  }
  return destination;
}
//继承实现时如：
b.prototype = Object.extend(new a(),{}}

/*
*第三种方法
*/
var a = Class.create();
a.prototype = {
	initialize:function(param){
		this.init(param);
	},
	init:function(param){
		this.param1 = document.createElement(ui);
	}
}

var b = Class.create();
b.prototype = Object.extend(new a(),{
	initialize:function(param){
		this.init(param);
		this.param2 = document.createElement(ui);
	}
})

var c = Class.create();
c.prototype = Object.extend(new b(),{
	initialize:function(param){
		//this.init(param);
	}
})
var b1 = new b("div");
var b2= new b("div");
var c1 = new c("div");
var c2 = new c("div");

alert(b1.param1 == b2.param1);//return false
alert(c1.param2 == c2.param2);//return true

var c = Class.create();   
c.prototype = Object.extend(new b(),{   
    initialize:function(param){   
        //this.init(param);   
    }   
})   

var Animal = new Class({   
    initialize: function(age){   
        this.age = age;   
    }   
});   
var Cat = Animal.extend({   
    initialize: function(name, age){   
        this.parent(age); //will call the previous initialize;   
        this.name = name;   
    }   
});