/*扩展Object类，添加Clone，JS实现克隆的方法*/
Object.prototype.Clone = function(){
  var objClone;
  if (this.constructor == Object){
    objClone = new this.constructor(); 
  }else{
    objClone = new this.constructor(this.valueOf()); 
  }
  for(var key in this){
    if ( objClone[key] != this[key] ){ 
      if ( typeof(this[key]) == 'object' ){ 
        objClone[key] = this[key].Clone();
      }else{
        objClone[key] = this[key];
      }
    }
  }
  objClone.toString = this.toString;
  objClone.valueOf = this.valueOf;
  return objClone; 
}
/*扩展Object类，添加Extend方法来实现JS继承, 目标对象将拥有源对象的所有属性和方法*/
Object.prototype.Extend = function (objDestination, objSource) {
  for (var key in objSource) {
    if (objSource.hasOwnProperty(key) && objDestination[key] === undefined) {
      objDestination[key] = objSource[key];
    }
  }
  return objDestination;
}

/*定义一个Person类*/
 function Person(_name,_age){
   this.name = _name;
   this.age = _age;
}

document.write("<pre>");
var p = new Person("孤傲苍狼",24);//创建一个人，名字是孤傲苍狼
var cloneP = p.Clone();//p调用在Object类中定义的Clone方法来克隆自己，如果能得到一个cloneP，那就证明了Person类确实是继承了Object类，所以就拥有了Clone
document.writeln("p是使用Person类以构造函数的方式创建出来的对象，p.name = "+p.name+"，p.age = "+p.age);
document.writeln("cloneP是p调用Clone方法克隆出来的对象，cloneP.name = "+cloneP.name+"，cloneP.age = "+cloneP.age);
document.writeln("cloneP对象和p对象是两个相互独立的对象，这两个对象的内存地址肯定是不相等，p == cloneP的结果是："+(p == cloneP));
cloneP.name="白虎神皇";//修改cloneP的名字
document.writeln("cloneP的name被修改了，cloneP.name = "+cloneP.name);
document.writeln("cloneP的name修改了，但是不影响到p，p.name = "+p.name);
document.write("</pre>");

/*定义一个Person类*/
function Person(_name,_age){
   this.name = _name;
   this.age = _age;
}
Person.prototype = new Object();//让Person类继承Object类

var p = new Person("孤傲苍狼",24);//创建一个人，名字是孤傲苍狼
alert("p.__proto__ === Person.prototype的结果是："+(p.__proto__ === Person.prototype));

<script type="text/javascript">
    var Person = function () { };
    Person.prototype.Say = function () {
      alert("Person say");
    }
    var p = new Person();
    p.Say();
</script>

Person.prototype.Say=function(){
    alert("Person say");
};

<script type="text/javascript">
    var Person = function () { };
    Person.prototype.Say = function () {
      alert("Person say");
    }
    Person.prototype.Salary = 50000;
    var Programmer = function () { };
    Programmer.prototype = new Person();//让程序员类从人这个类继承
    Programmer.prototype.WriteCode = function () {
      alert("programmer writes code");
    };
    Programmer.prototype.Salary = 500;
    var p = new Programmer();
    p.Say();
    p.WriteCode();
    alert(p.Salary);
</script>

var p1=new Person();
Programmer.prototype=p1;

p1.__proto__=Person.prototype;
Programmer.prototype.__proto__=Person.prototype;

function getProperty(obj, prop) {
  if (obj.hasOwnProperty(prop))
    return obj[prop];
  else if (obj.__proto__ !== null)
    return getProperty(obj.__proto__, prop);//递归
  else
    return undefined;
}

<script type="text/javascript">
  /*查找obj对象的prop属性*/
   function getProperty(obj, prop) {
    if (obj.hasOwnProperty(prop))
      return obj[prop];
    else if (obj.__proto__ !== null)
      return getProperty(obj.__proto__, prop);//递归
    else
      return undefined;
  }
  var Person = function () { };//定义Person类
  Person.prototype.Say = function () {
    alert("Person say");
  }
  Person.prototype.Salary = 50000;
  var Programmer = function () { };//定义Programmer类
  //Programmer.prototype = new Person();//让程序员类从人这个类继承，写法一
  Programmer.prototype = Person.prototype;//让程序员类从人这个类继承，写法二
  Programmer.prototype.WriteCode = function () {
    alert("programmer writes code");
  };
  Programmer.prototype.Salary = 500;
  var p = new Programmer();
  var SayFn = getProperty(p,"Say");//查找p对象的Say方法
  SayFn.call(p);//调用找到的Say方法
</script>