javascript - __proto__ 和 JavaScript 中的继承

Question

我已经研究了几天 JavaScript 继承，虽然我已经取得了很大的进步，但有些事情我还不太明白。

例如，我发现这种行为非常令人困惑:

var Employee = function Employee() { this.company = 'xyz'; };
var Manager = function Manager() { this.wage = 'high'; };

var m = new Manager();

m; // { "wage": "high", __proto__ : Manager } -- no problems so far.

Manager.prototype = new Employee();

var n = new Manager;

m.company; // undefined
n.company; // "xyz"

m 的 __proto__ 属性指向一个不是 Manager 的 current 原型(prototype)的对象。这有点违反直觉，因为:

An object inherits properties even if they are added to its prototype after the object is created.

Taken from JavaScript: The Definitive Guide, 5th Edition, By David Flanagan

难道这种行为不也适用于上述案例吗？

谁能澄清一下？

Answer 1

这有点令人困惑，因为函数本身就是对象:

function Employee() {this.company = 'xyz';}
function Manager() {}

var m = new Manager();
Manager.prototype = new Employee();

/* You set the prototype on the Manager function (object), 
   your m instance and Manager function are separate objects.
   At this point the prototype of m is still undefined */

m = new Manager();
m.company; // 'xyz'

/* Creating a new Manager copies the new prototype */