//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