节点js文件中有多个module.exports

Question

How does the Nodejs engine decides when a file has multiple module.exports and it is being required by another file ? How does the final closure is being calculated ?

Answer 1

It uses the value that module.exports has when the execution of the module has finished:

module.exports = { foo: 'bar' };
module.exports = { a: 17.8 };    // overwrite "module.exports"
module.exports = 5;              // and again 
module.exports = { b: 123 };     // and again

Now, when you require the module, you will get { b: 123 } .

module.exports is not a magic keyword, it's just a variable that you can set to tell NodeJS what should be exported.