javascript - What is the purpose of Node.js module.exports and how do you use it?

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What is the purpose of Node.js
module.exports and how do you use
it?

I can't seem to find any
information on this, but it appears to be a rather important part of Node.js as I often
see it in source code.

According to the href="http://nodejs.org/docs/v0.4.2/api/globals.html#module" rel="noreferrer">Node.js
documentation:

module

A reference to the current
module. In
particular module.exports
is the same as the exports
object. See

src/node.js for more
information.

But
this doesn't really help.

What exactly does
module.exports do, and what would a simple example
be?

Answer

href="http://nodejs.org/api/modules.html#modules_module_exports"
rel="noreferrer">module.exports is the object
that's actually returned as the result of a require
call.

The exports
variable is initially set to that same object (i.e. it's a shorthand "alias"), so in the
module code you would usually write something like
this:

let myFunc1 =
            function() { ... };
let myFunc2 = function() { ...
            };
exports.myFunc1 = myFunc1;
exports.myFunc2 =
            myFunc2;

to export (or
"expose") the internally scoped functions myFunc1 and
myFunc2.

And in the
calling code you would
use:

const m =
            require('./mymodule');
m.myFunc1();

where
the last line shows how the result of require is (usually) just
a plain object whose properties may be
accessed.

NB: if you overwrite
exports then it will no longer refer to
module.exports. So if you wish to assign a new object (or a
function reference) to exports then you should also assign that
new object to
module.exports

/>

It's worth noting that the name added to
the exports object does not have to be the same as the module's
internally scoped name for the value that you're adding, so you could
have:

let myVeryLongInternalName =
            function() { ... };
exports.shortName = myVeryLongInternalName;
//
            add other objects, functions, as
            required

followed
by:

const m =
            require('./mymodule');
m.shortName(); // invokes
            module.myVeryLongInternalName