目录作为模块
将程序和库组织到自包含目录中,然后为这些目录提供单个入口点是很方便的。
可以通过三种方式将文件夹作为参数传给 require()
。
首先是在文件夹的根目录创建 package.json
文件,指定 main
模块。
一个示例 package.json
文件可能如下所示:
{ "name" : "some-library",
"main" : "./lib/some-library.js" }
如果这是在 ./some-library
的文件夹中,则 require('./some-library')
将尝试加载 ./some-library/lib/some-library.js
。
这就是 Node.js 中对 package.json
文件的认识程度。
如果目录中不存在 package.json
文件,或者 "main"
条目丢失或无法解析,则 Node.js 将尝试从该目录中加载 index.js
或 index.node
文件。
例如,如果前面的示例中没有 package.json
文件,则 require('./some-library')
将尝试加载:
./some-library/index.js
./some-library/index.node
如果这些尝试失败,Node.js 将报告整个模块丢失,并显示默认错误:
Error: Cannot find module 'some-library'
It is convenient to organize programs and libraries into self-contained
directories, and then provide a single entry point to those directories.
There are three ways in which a folder may be passed to require()
as
an argument.
The first is to create a package.json
file in the root of the folder,
which specifies a main
module. An example package.json
file might
look like this:
{ "name" : "some-library",
"main" : "./lib/some-library.js" }
If this was in a folder at ./some-library
, then
require('./some-library')
would attempt to load
./some-library/lib/some-library.js
.
This is the extent of the awareness of package.json
files within Node.js.
If there is no package.json
file present in the directory, or if the
"main"
entry is missing or cannot be resolved, then Node.js
will attempt to load an index.js
or index.node
file out of that
directory. For example, if there was no package.json
file in the previous
example, then require('./some-library')
would attempt to load:
./some-library/index.js
./some-library/index.node
If these attempts fail, then Node.js will report the entire module as missing with the default error:
Error: Cannot find module 'some-library'