理解prototype

从别人的博客里面盗了2张图，这2张图将对象/实例/prototype/__proto__/constructor之间的关系描绘的很清楚。

1.prototype 为 function的属性，实例化的对象（即new之后的对象）没有prototype，只有__proto__,且指向声明该实力对象函数的prototype

2.babel 继承源码分析：

class Base{
  constructor(){
    this.myname = 'jack';
  }
}
Base.$inject = ['$http']
Base.prototype.age = 10;
class HostController extends Base{

}

编译后：

'use strict';

function _possibleConstructorReturn(self, call) { if (!self) { throw new ReferenceError("this hasn't been initialised - super() hasn't been called"); } return call && (typeof call === "object" || typeof call === "function") ? call : self; }

function _inherits(subClass, superClass) {
    if (typeof superClass !== "function" && superClass !== null) { throw new TypeError("Super expression must either be null or a function, not " + typeof superClass); }
　　//继承父类的原型方法
    subClass.prototype = Object.create(superClass && superClass.prototype, { constructor: { value: subClass, enumerable: false, writable: true, configurable: true } });
　　//关键步骤，通过__proto__指向父类构造函数，实现父类静态属性，方法的继承
    if (superClass) Object.setPrototypeOf ? Object.setPrototypeOf(subClass, superClass) : subClass.__proto__ = superClass;
}
//该方法就是判断 实例所属
function _classCallCheck(instance, Constructor) { if (!(instance instanceof Constructor)) { throw new TypeError("Cannot call a class as a function"); } }

var Base = function Base() {
    _classCallCheck(this, Base);

    this.myname = 'jack';
};

Base.$inject = ['$http'];
Base.prototype.age = 10;

var HostController = function(_Base) {
    _inherits(HostController, _Base);

    function HostController() {
        _classCallCheck(this, HostController);

        return _possibleConstructorReturn(this, (HostController.__proto__ || Object.getPrototypeOf(HostController)).apply(this, arguments));
    }

    return HostController;
}(Base);

3.es6 中class extends 继承，不仅继承了父类在构造函数中定义的属性方法，还可以继承父类原型链上的属性和方法，最后还有，父类定义的静态属性和方法也能继承，只不过子类调用父类的静态方法必须写为：Child.xxx(子类.父类属性或方法)。

　　

class Base{
    constructor(){
        this.name = 'jack'
    }
    say(){
        console.log('.............');
    }
}

Base.inject = ['Base'];
Base.prototype.age = 10;


class Child extends Base{

}

var c = new Child();
c.name;
c.say();
Child.inject;

 4.在babel继承中，使用到了Object.setPrototypeOf()方法，该方法有2个参数：

　　Object.setPrototypeOf(obj,prototype):obj代表要目标对象，将prototype参数指定的对象赋给obj的__proto__，等同于：obj.__proto__ = prototype;

http://www.cnblogs.com/xiaohuochai/p/5721552.html