function Rectangle()
{
    this.width = 0;
    this.height = 0;
    this.area = function(){ return this.width * this.height;};
}

var o = new Object();
Rectangle.apply(o);
o.width = 10;
o.height = 20;
alert(o.area());

var Class = {
    create : function(){
        return function(){
            this.initialize.apply(this,arguments);
        }
    }
}

//创建类
var Rectangle = Class.create();
Rectangle.prototype = {
    initialize : function(width,height){
        this.width = width;
        this.height = height;
    },
    toString : function(){
        return "width:" + this.width + "\r\n" + "height:" + this.height;
    }
}

//实例化对象并初始化
var rectangle = new Rectangle(80,120);
alert(rectangle.toString());