javascript - 难以理解 JavaScript 中的基本对象工作原理

Question

我正在学习 JavaScript，我正在使用的书中有一个我不理解的示例。 是这样的:

var chineseBox = {};
chineseBox.content = chineseBox;

然后书中列出了两个表达式和它们的值。首先，"content' in chineseBox; 返回 true。然后，我没有得到的，"content"in chineseBox.content这也返回 true。 我认为如果第二个表达式的计算结果为 false 会更自然，指向之前定义的空 chineseBox 对象。 有理由这样工作吗？此功能的实际含义是什么？ 我如何探索对象的更深层次？ chineseBox.content.content 对吗？

Answer 1

I think it'd be more natural if the second expression evaluated to false, pointing to the empty chineseBox object defined earlier.

它不再是空的。从 chineseBox.content = chineseBox 开始，它现在有一个属性。

当您将对象引用分配给事物(变量、属性等)时，存储的值是对象的引用，而不是对象的副本。所以 chineseBox(变量)和 chineseBox.content(属性)都指向 同一个 对象，它有一个名为 的属性内容.

让我们在此添加一些 ASCII 艺术:

var chineseBox = {};

这给了我们:

+−−−−−−−−−−−−−−−−−−−−−−−+
| chineseBox (variable) |
+−−−−−−−−−−−−−−−−−−−−−−−+          +−−−−−−−−−−−−−−−+
| value                 |−−−−−−−−−>|    (object)   |
+−−−−−−−−−−−−−−−−−−−−−−−+          +−−−−−−−−−−−−−−−+
                                   |               |
                                   +−−−−−−−−−−−−−−−+

Now we do

chineseBox.content = chineseBox;

...我们有:

                                            /−−−−−−−−−−−\
+−−−−−−−−−−−−−−−−−−−−−−−+                   |           |
| chineseBox (variable) |                   v           |
+−−−−−−−−−−−−−−−−−−−−−−−+          +−−−−−−−−−−−−−−−+    |
| value                 |−−−−−−−−−>|    (object)   |    |
+−−−−−−−−−−−−−−−−−−−−−−−+          +−−−−−−−−−−−−−−−+    |
                                   |  content      |−−−−/
                                   +−−−−−−−−−−−−−−−+

只有一个对象。有两个引用指向它。