如何在javascript中访问对象原型？ [英] How to access object prototype in javascript?

问题描述

在所有文章中都写道，JavaScript是一种基于原型的语言，这意味着每个对象都有一个原型（或更确切地说，原型链）。

In all the articles it is written that JavaScript is a prototype-based language, meaning that every object has a prototype (or, more precisely, prototype chain).

到目前为止，我已经尝试了以下代码片段：

So far, I've tried the following code snippet:

var F = function();
F.prototype.member1 = 1;
var object1 = new F();
console.log(object1.member1); // prints 1

如何访问 object1的原型对象？是否存在与浏览器无关的方式（我的意思是，不依赖于 __ proto __ 属性？看到这个链接，但也许自2010年以来有新的发展）如果我不能，你能不能分享一下背后的理由引擎盖？

How can I access the prototype object of object1? Is there a browser-neutral way to do that (I mean, not relying on __proto__ property? Seen this link, but maybe there are new developments since 2010) If I can't, could you share please the rationale behind the hood?

推荐答案

var f = function();
var instance = new f();

如果您知道实例的名称 类函数，你可以简单地访问原型：

If you know name of instance class function, you can simply access prototype as:

var prototype = f.prototype;
prototype.someMember = someValue;

如果您不这样做：

1）

var prototype = Object.getPrototypeOf(instance);
prototype.someMember = someValue;

2）或

var prototype = instance.__proto__;
prototype.someMember = someValue;

3）或

var prototype = instance.constructor.prototype; // works only if constructor is properly assigned and not modified
prototype.someMember = someValue;

为了兼容性，您可以在代码中放入以下代码段（并始终使用 Object.getPrototypeOf（instance）返回原型）：

For compatibility you can place into your code the following snippet (and use always Object.getPrototypeOf(instance) to return prototype):

if(!Object.getPrototypeOf) {

  if(({}).__proto__ === Object.prototype && ([]).__proto__ === Array.prototype) {

    Object.getPrototypeOf = function getPrototypeOf(object) {
      return object.__proto__;
    };

  } else {

    Object.getPrototypeOf = function getPrototypeOf(object) {

      // May break if the constructor has been changed or removed
      return object.constructor ? object.constructor.prototype : void 0;

    };

  }
}

更新：

根据ECMA-262第6版（2015年6月） __ proto __ 属性被标准化为Web的附加功能浏览器。所有最新版本的顶级浏览器现在都支持它。了解更多关于 __ proto __ ：

According to ECMA-262 6th Edition (June 2015) __proto__ property is standardized as additional feature for Web browsers. All latest editions of top browsers supports it now. Read more about __proto__:

• MDN： Object.prototype .__ proto __

EDMA-262第6版（2015年6月）： B.2.2.1 Object.prototype .__ proto __

EDMA-262 6th Edition (June 2015): B.2.2.1 Object.prototype.__proto__

这篇关于如何在javascript中访问对象原型？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！