Difference between "exports" and "module.exports"

In node, if we want to something to be acessible outside, we should export it by assigning it to an attribute of exports or module.exports. So we can use it by simply requireing it in other files.

But, sometimes we want to use require like importing a function. Rookies might write something like these. 

1
2
3
exports = function() {
    // something
};

But this approach will certainly fail. Actually if you want to export a function use module.exports, instead of exports.

The reason lies in the implementation of Node’s module. In Node, every source file is a independent module. The module object definition is like below, we’ll just focus on exports. 

1
2
3
4
5
6
function Module(id, parent) {
    this.id = id;
    this.exports = {};
    this.parent = parent;
    // something else
}

And when Node compile your source file, it will wrap it first. 

1
2
3
(function (exports, require, module, __filename, __dirname) {
  // your codes
})

Then node will call this function and pass those parameters to it, so we can use them in our files. The exports is the shortcut for module.exports. So even if you reassign it a new value, the original object module.exports won’t be affected at all.

Conclusion

In a nutshell exports is just a reference to module.exports, don’t assign it a new value. Instead use this. 

1
2
3
exports = module.exports = function() {
  //blahblah
}