//囚犯示例 
//1.定义原型对象 
var proto = { 
 sentence : 4, //监禁年限 
 probation: 2 //缓刑年限 
}; 
//2.定义原型对象的构造函数 
var Prisoner = function(name, id) { 
 this.name = name; 
 this.id = id; 
}; 
//3.将构造函数关联到原型 
Prisoner.prototype = proto; 
//4.实例化对象——采用工厂函数实例化对象 
var makePrisoner = function(name, id) { 
 //采用工厂函数实力化对象prisoner 
 var prisoner = Object.create( proto ); 
 prisoner.name = name; 
 prisoner.id = id; 
 return prisoner; 
}; 
 
var firstPrisoner = makePrisoner( 'Joe', '12A' ); 
 
//firstPrisoner.sentence在firstPrisoner对象找不到sentence属性， 
//所以查找对象的原型并找到了Both of these output 4 
console.log( firstPrisoner.sentence ); 
console.log( firstPrisoner.__proto__.sentence ); 
//把对象的sentence属性设置为10 
firstPrisoner.sentence = 10; 
//outputs 10 
//确定对象上的属性值已设置为10 
console.log( firstPrisoner.sentence ); 
//但是对象的原型并没有变化，值仍然为4 
console.log( firstPrisoner.__proto__.sentence ); 
//为了使获取到的属性回到原型的值，将属性从对象上删除 
delete firstPrisoner.sentence; 
//接下来，JavaScript引擎在对象上不能再找到该属性， 
//必须回头去查找原型链，并在原型对象上找到该属性 
// Both of these output 4 
console.log( firstPrisoner.sentence ); 
console.log( firstPrisoner.__proto__.sentence );

xxh@xxh-E440:~/workspace$ node t6 
4 
4 
10 
4 
4 
4