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当文件直接从 Node.js 运行时,则 require.main
被设置为其 module
。
这意味着可以通过测试 require.main === module
来确定文件是否被直接运行。
对于文件 foo.js
,如果通过 node foo.js
运行,则为 true
,如果通过 require('./foo')
运行,则为 false
。
因为 module
提供了 filename
属性(通常相当于 __filename
),通过查看 require.main.filename
就可以得到当前应用的入口点。
When a file is run directly from Node.js, require.main
is set to its
module
. That means that it is possible to determine whether a file has been
run directly by testing require.main === module
.
For a file foo.js
, this will be true
if run via node foo.js
, but
false
if run by require('./foo')
.
Because module
provides a filename
property (normally equivalent to
__filename
), the entry point of the current application can be obtained
by checking require.main.filename
.