node.js 相当于 python 的 if __name__ == '__main__'
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node.js equivalent of python's if __name__ == '__main__'
提问by nornagon
I'd like to check if my module is being included or run directly. How can I do this in node.js?
我想检查我的模块是否被包含或直接运行。我怎样才能在 node.js 中做到这一点？
回答by Stephen Emslie
The docsdescribe another way to do this which may be the preferred method:
文档描述了另一种方法，这可能是首选方法：
When a file is run directly from Node, require.main is set to its module.
当一个文件直接从 Node 运行时，require.main 被设置为它的模块。
To take advantage of this, check if this module is the main module and, if so, call your main code:
要利用这一点，请检查此模块是否是主模块，如果是，请调用您的主代码：
var fnName = function() {
// main code
}
if (require.main === module) {
fnName();
}
EDIT: If you use this code in a browser, you will get a "Reference error" since "require" is not defined. To prevent this, use:
编辑：如果您在浏览器中使用此代码，由于未定义“require”，您将收到“参考错误”。为了防止这种情况，请使用：
if (typeof require !== 'undefined' && require.main === module) {
fnName();
}
回答by nornagon
if (!module.parent) {
// this is the main module
} else {
// we were require()d from somewhere else
}
EDIT: If you use this code in a browser, you will get a "Reference error" since "module" is not defined. To prevent this, use:
编辑：如果您在浏览器中使用此代码，您将收到“参考错误”，因为“模块”未定义。为了防止这种情况，请使用：
if (typeof module !== 'undefined' && !module.parent) {
// this is the main module
} else {
// we were require()d from somewhere else or from a browser
}
