Javascript 这个Node.js代码似乎取代了同一个函数中的函数实现，它是做什么的？ 我试图调试一大堆NoDE.js代码，下面的代码看起来很疯狂（因为我的C++和C语言的经验）。有很多函数如下所示： function _builderUtil() { const data = require("builder-util"); _builderUtil = function () { return data; }; return data; }

。。。我不知道要搜索什么才能得到更多的细节

这是我在这里看到的。。。有一个名为

\u builderUtil（）

的函数，其中有一个

require（）

调用，该调用应加载指定的模块。然后还有第二个

\u builderUtil

函数中的内容。它看起来像一个包含匿名函数引用的变量。或者，这可能会取代外部函数实现

这个内部函数（看起来是匿名的）的目的是什么？这段代码是做什么的，在Node.js中是如何调用的，这样我就知道要搜索什么了

或者，这可能会取代外部函数实现

这就是它所做的。第一次调用

\u builderUtil

时，它执行

require

调用，并将结果保存在本地

数据

常量中。然后，它用一个只返回

data

常量的函数覆盖执行该操作的函数。（由于内部函数关闭，

data

常量仍然存在。）

基本上，它通过

require

延迟加载数据，然后每次加载后调用它时都返回相同的数据

正如CertainPerformance在评论中指出的，这是不必要的。js的模块系统维护一个加载模块的缓存，因此在每次需要数据时只需使用

require（“builder util”）

就足够了，而不是调用

\u builderUtil

但是回到它的工作方式，忽略

的细节需要
：

最初，内存中有类似的内容：

+−−−−−−−−−−−−+
_builderUtil−−−−−>| (function) |
                  +−−−−−−−−−−−−+
                  | [code]     |
                  +−−−−−−−−−−−−+
然后，该函数用一个新函数覆盖
\u builderUtil
，该函数只返回
数据。函数有一个指向创建它们的环境对象的链接，因此一旦调用完成，您就有以下内容：

+−−−−−−−−−−−−+
                  | (function) |  (the old function, ready to be garbage−collected)
                  +−−−−−−−−−−−−+
                  | [code]     |
                  +−−−−−−−−−−−−+

                         +−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
                         |                               |
                         v                               |
                  +−−−−−−−−−−−−−−+                       |
                  | (env object) |                       |
                  +−−−−−−−−−−−−−−+      +−−−−−−−−−−−−−+  |
                  | data         |−−−−−>| (some data) |  |
                  +−−−−−−−−−−−−−−+      +−−−−−−−−−−−−−+  |
                                                         |
                  +−−−−−−−−−−−−−−−+                      |
_builderUtil−−−−−>|   (function)  |                      |
                  +−−−−−−−−−−−−−−−+                      |
                  | [environment] |−−−−−−−−−−−−−−−−−−−−−−+
                  | [code]        |
                  +−−−−−−−−−−−−−−−+
+−−−−−−−−−−−−+
|（函数）|（旧函数，准备成为垃圾−（收集）
+−−−−−−−−−−−−+
|[守则]|
+−−−−−−−−−−−−+
+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
|                               |
五|
+−−−−−−−−−−−−−−+                       |
|（环境物体）||
+−−−−−−−−−−−−−−+      +−−−−−−−−−−−−−+  |
|资料|−−−−−>| (部分数据)|
+−−−−−−−−−−−−−−+      +−−−−−−−−−−−−−+  |
|
+−−−−−−−−−−−−−−−+                      |
_建筑工地−−−−−>|   （功能）||
+−−−−−−−−−−−−−−−+                      |
|[环境]|−−−−−−−−−−−−−−−−−−−−−−+
|[守则]|
+−−−−−−−−−−−−−−−+
最终，垃圾收集发生了，您只需要

+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
                         |                               |
                         v                               |
                  +−−−−−−−−−−−−−−+                       |
                  | (env object) |                       |
                  +−−−−−−−−−−−−−−+      +−−−−−−−−−−−−−+  |
                  | data         |−−−−−>| (some data) |  |
                  +−−−−−−−−−−−−−−+      +−−−−−−−−−−−−−+  |
                                                         |
                  +−−−−−−−−−−−−−−−+                      |
_builderUtil−−−−−>|   (function)  |                      |
                  +−−−−−−−−−−−−−−−+                      |
                  | [environment] |−−−−−−−−−−−−−−−−−−−−−−+
                  | [code]        |
                  +−−−−−−−−−−−−−−−+
+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
|                               |
五|
+−−−−−−−−−−−−−−+                       |
|（环境物体）||
+−−−−−−−−−−−−−−+      +−−−−−−−−−−−−−+  |
|资料|−−−−−>| (部分数据)|
+−−−−−−−−−−−−−−+      +−−−−−−−−−−−−−+  |
|
+−−−−−−−−−−−−−−−+                      |
_建筑工地−−−−−>|   （功能）||
+−−−−−−−−−−−−−−−+                      |
|[环境]|−−−−−−−−−−−−−−−−−−−−−−+
|[守则]|
+−−−−−−−−−−−−−−−+
尽管看起来很奇怪，为什么不直接使用
函数_builderUtil（）{return require（“builder util”）}
？多次
require
调用不会再次运行其他模块的顶级代码，对吗？将其保存在变量中并重新分配函数有什么意义？（除非
builder util
在初始化后重新分配其导出，因此需要保存初始值，这真的很奇怪）@CertainPerformance-是的，我怀疑编写它的人不理解Node.js的模块缓存。：-）或者，他们希望创建一个抽象，这样您就不必在每次需要数据时都记住名称
“builder util”
（而不是
“builderutil”
或
“builder utils”
，等等）。（但即便如此，他们也可以让它每次调用
require
）
+−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−+
                         |                               |
                         v                               |
                  +−−−−−−−−−−−−−−+                       |
                  | (env object) |                       |
                  +−−−−−−−−−−−−−−+      +−−−−−−−−−−−−−+  |
                  | data         |−−−−−>| (some data) |  |
                  +−−−−−−−−−−−−−−+      +−−−−−−−−−−−−−+  |
                                                         |
                  +−−−−−−−−−−−−−−−+                      |
_builderUtil−−−−−>|   (function)  |                      |
                  +−−−−−−−−−−−−−−−+                      |
                  | [environment] |−−−−−−−−−−−−−−−−−−−−−−+
                  | [code]        |
                  +−−−−−−−−−−−−−−−+