prototype与__proto__区别

   参考链接：http://www.voidcn.com/article/p-okxoiaoj-bad.html

  　　　　　 https://stackoverflow.com/questions/9959727/proto-vs-prototype-in-javascript

  一：__proto__和prototype

参考下面的回答：

__proto__ is the actual object that is used in the lookup chain to resolve methods, etc. prototype is the object that is used to build __proto__ when you create an object with new:

( new Foo ).__proto__ === Foo.prototype
( new Foo ).prototype === undefined

The prototype is a property on a constructor function that sets what will become the __proto__ property on the constructed object.

 就是说真正的原型链就是通过__proto__来连起来的。

 比如下面的例子，animal通过__proto__-->f(){ [native code] }-->object-->null,,一路走到null

function animal(){}

var dog = new animal();

console.log(dog.prototype)  //undefined

console.log(dog.__proto__);  //constructor:f animal()
console.log(animal.prototype) //constructor:f animal()
console.log(animal.__proto__);  //f(){ [native code] }

console.log(animal.prototype === dog.__proto__); //true

console.log(animal.__proto__.__proto__); //Object

console.log(animal.__proto__.__proto__.__proto__);   //null

console.log(animal.prototype.prototype); //undefined

 二：修改__proto__

       上面直接修改__proto__是不安全的（这东西只是浏览器自己实现的一个属性），正确修改原型的方式像下面这样：

function inherits(Child, Parent) {
    var F = function () {};
    F.prototype = Parent.prototype;
    Child.prototype = new F();
    Child.prototype.constructor = Child;
}

inherits(Child,Base);

   现在可以使用ES6的Object.create 和 Object.setPrototypeOf来修改prototype