[英]__proto__ and inheritance in JavaScript
I've been studying JavaScript inheritance for a couple of days, and although I've made quite a lot of progress there are some things I don't quite understand yet.这几天我一直在研究 JavaScript 继承,虽然我已经取得了很大的进步,但有些事情我还不是很明白。
For example, I find this behaviour quite confusing:例如,我发现这种行为很令人困惑:
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
's __proto__
property points to an object which is not Manager
's current prototype. m
的__proto__
属性指向一个不是Manager
的当前原型的对象。 This is a little counterintuitive, given that: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.
对象继承属性,即使它们是在创建对象后添加到其原型中的。
Taken from JavaScript: The Definitive Guide, 5th Edition, By David Flanagan
摘自JavaScript:权威指南,第 5 版,作者:David Flanagan
Couldn't this behaviour be applied to the aforementioned case, too?难道这种行为也不能适用于上述案例吗?
Can anyone clarify?谁能澄清一下?
It's a little confusing because functions are themselves objects: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 */
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