Javascript对象属性存在奇怪的平等问题 [英] Strange equality issue with Javascript object properties

问题描述

为什么在执行该代码片段之后：

Why after executing that snippet of code:

var a = {};
var b = {};

var g = {};
g[a] = "aa";
g[b] = "dd";

g [a]的值是dd？

the value of g[a] is "dd"?

a == b是假的，所以这里发生了什么？

a == b is false so what is going on here?

推荐答案

JavaScript对象键只能是字符串。当您存储 g [a] ='aa'时，使用 toString（）方法将a转换为字符串， ¹ 所以你实际上在 g [a.toString（）] 'aa' $ c>。

JavaScript object keys can only be strings. When you store g[a] = 'aa', a is converted to a string using the toString() method,¹ so you're actually storing 'aa' at g[a.toString()].

在这种情况下， a.toString（）是'[ object Object]'，等于 b.toString（）。

In this case, a.toString() is '[object Object]', which is equal to b.toString().

为了使它真的很明显，你问题中的代码等同于：

To make it really obvious, the code in your question is equivalent to this:

var g = {};
g['[object Object]'] = 'aa';
g['[object Object]'] = 'dd';

故事的道德：只是不要尝试使用字符串以外的任何东西作为属性名称。

Moral of the story: just don't try to use anything other than strings as property names.

_{¹ 来源： MDC：JavaScript Member Operators - Property Names}

_{¹Source: MDC: JavaScript Member Operators - Property Names}

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