How do I export a JavaScript class in Node.js?

In its simplest form, here is the issue where a class will not be correctly returned exported if it is a class.

app.js

var Users = require('./users.js');
Users.find('test');

users.js

var Users = function() {
  function Users() {
    console.log('Users Initiated');
  }

  Users.prototype.find = function(username) {
    console.log(username);
  };

  return Users;

}

module.exports = Users;

The error I receive in the console

/Users/me/nodejsClassExport/app.js:2
Users.find('test');
      ^
TypeError: Object function () {
  function Users() {
    console.log('Users Initiated');
  }

  Users.prototype.find = function(username) {
    console.log(username);
  };

  return Users;

} has no method 'find'
    at Object.<anonymous> (/Users/me/nodejsClassExport/app.js:2:7)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)
    at startup (node.js:119:16)
    at node.js:906:3

How do I export it correctly so it can be used without crashing?

You're "Users" object is a function, a constructor apparently. You can't get to methods of a constructor's prototype from the constructor directly like that. You can however create an instance and access the prototypes that way.

var u = new Users();
u.find(whatever);

edit — now, back in the module, you've got two "Users" symbols. One is that outer function, and the other is that "Users" function declared inside it. However, what you export is the outer one, and it doesn't have a "find" method on its prototype. You can solve this problem by calling the outer "Users" function to get to the proper one. That can be done either in the module or in the client context, though I suspect you probably want it in the module:

module.exports = Users();

From the documentation:

The module.exports object is created by the Module system. Sometimes this is not acceptable; many want their module to be an instance of some class. To do this assign the desired export object to module.exports. Note that assigning the desired object to exports will simply rebind the local exports variable, which is probably not what you want to do.

So replace

exports = Users;

with

module.exports = Users;

There is a problem with this line:

this.users = nStore["new"]('data/users.db');

It is either not saving a new object to this.users or it falling victim to an asynchronous race condition, as it is complaining about how this.users.find() does not exist.

Likely, it is because that function for nStore takes a callback, so you'll have to consider that with the rest of your code.

this.users = nStore.new('data/users.db', function () {
  console.log('Users Initiated');
  // now it is safe to use the methods in 'this.users'
});