function test(message){
     alert(message);
   }
   var f = test;
   f('hello world');

var f = function(message){
     alert(message);   
   };
f('hello world');

var f = new Function("message","alert(message);");
f('hello world');

function test(){
     this.property = 'hello world';

   }
   test();
   alert(window.property);  //由于在全局范围内调用，test函数中的this实际指向全局对象(window)

   var obj = {};
   test.call(obj);   //通过call第一个参数指定执行上下文范围，所以test函数中this指向obj实例。
   alert(obj.property);   

   var obj2 = {};
   obj2.test2 = test;   //将obj2实例方法test指向 全局test方法
   obj2.test2();      //由于是在obj2上调用test方法，所以test函数中的this也指向了obj2实例
   alert(obj2.property);

function Person(){
   this.name = 'xfrog';
   this.Say = function(){
     alert(this.name);
   };
}

var p1 = new Person();
p1.Say();

Person();
Say();
window.Say();

var p1 = new Person();
var p2 = new Person();
var test = p1.Say == p2.Say;

function Person(){
     this.name = 'xfrog';
     this.Say = say;   
   }

   function say(){
     alert(this.name);   
   }

   var p1 = new Person();
   var p2 = new Person();
   alert(p1.Say == p2.Say);
   p1.name = 'wang';
   p1.Say();

function Person(){

   }
   Person.prototype.name = 'xfrog';
   Person.prototype.Say = function(){
     alert(this.name);
   };

   var p1 = new Person();
   var p2 = new Person();
   alert(p1.Say == p2.Say);   //返回true

function Person(){
     this.name = 'wang';
   }

   Person.prototype.name = 'xfrog';
   Person.prototype.Say = function(){
     alert(this.name);
   }

   var p1 = new Person();
   p1.Say();   //将返回wang

p1.__proto__["Say"]();

function Person(){

   }

   Person.prototype = {name:'xfrog', Say:function(){
     alert(this.name);
   }};

Person.prototype = { 
     constructor: Person,
     name :'xfrog',
     Say:function(){
        alert(this.name);
     }
   }

function Person(){
   }

   Person.prototype = {
     name: 'xfrog',
     obj : { age: 18 },
     Say : function(){
        alert(this.obj.age);
     }
   };

   var p1 = new Person();
   var p2 = new Person();
   p1.obj.age = 20;
   p1.Say();
   p2.Say();

function Person(){
     this.obj = { age: 18 };
   }