module.export function not returning results

Question

I'm having some problems returning results from a module function.
Below are two files that I'm working with.

When I call the exported function it returns nothings.
Any suggestions/fixes as to why? Does it have to do with callbacks?

models/index.js

module.exports = exports = function(library) {    
    modCodes.findOne({name: library}, {modcode:1}, function(err, mc) {
      if (err) throw new Error(err);
      var db = mongoose.createConnection('mongodb://localhost:27017/' + mc.modcode + '?safe=true');
      var models = {
        Books: db.model('books', require('./schemas/books'))
        }

        return models;
    });

};

books.js

var Models = require('../models');    
console.log(Models("myLibrary")); //return nothing

Solution

The reason you're getting no results is that you're trying to return a function value synchronously from an asynchronous callback. Instead of providing a function value, the return statement will instead stop the function, as return; would normally do. This is why you must use a callback for asynchronous operations:

module.exports = exports = function(library, callback) {
  modCodes.findOne({name: library}, {modcode: 1}, function (err, mc) {
    if (err) throw new Error(err);
    var db = mongoose.createConnection('mongodb://localhost:27017/' + mc.modcode + '?safe=true');
    var models = {
      Books: db.model('books', require('./schemas/books'))
    }
    callback(models);
  });
};

And this is how you would be able to use it:

var Models = require('../models');    
Models('myLibrary', function(models) {
  console.log(models);
});