原型链([[prototype]]或__proto__)

对象创建方式

1.对象直接量

var person={
    name="oBa";
    sex='man';
}

[[prototype]]指向Object.prototype

2.new方法,与1类似

var person=new Object();
person.name='oBa';
person.sex='man';

[[prototype]]指向Object.prototype

3.工厂方式 ,少见了

 var createPerson = function(name,age,job){
       var person = new Object();
       person.name = name;
       person.age = age;
       person.job = job;
       person.sayName = function(){
          alert(person.name);
       }
       return person;
    }
    
    var person1 = createPerson("oBa","18","mokey");
    person1.sayName(); //  oBa

person1的[[prototype]]指向Object.prototype

4.构造函数

function Person(name,age,job){   
    this.name = name; 
    this.age = age;
    this.job = job;
}; 
Person.prototype.sayName = function(){
        alert(this.name); 
};  
var person1 = new Person("oBa",18,"bape");
person1.sayName();

person1的[[prototype]]指向Person.prototype,
Person.prototype的[[prototype]]指向Object.prototype，
这里面多了一层，有new就是不一样

5.由Object.create()方法创建//es5

var person={
    name="oBa";
    sex='man';
}
var person1=Object.create(person);

person1的[[prototype]]指向person
Object.create()内部大概原理:

Object.create=function(p){
   function F(){};
   F.prototype=p;
   return new F();
}

.proto===.constructor.prototype不一定正确
例如一个对象通过Object.create()创建，则不成立