gistfile1.js

// account.js
var Store = new (require('./store').Store)('accounts', {'_id': 'id', 's': 'secret'}, function(){return new Account();});
  
var Account = function Account() {
  this.id = this.secret = null;
};

Account.findById = function(id, callback) {
  Store.findOne({'_id': Store.idFromString(id)}, function(err, result) {
    if (err) { callback(err); }
    else { callback(null, result); }
  });
};

module.exports = Account;


//store.js
var Mongo = require('mongodb'),
  Db = Mongo.Db,
  Connection = Mongo.Connection,
  Server = Mongo.Server,
  ObjectID = Mongo.BSONPure.ObjectID;
  
var db = new Db('mongo_stats', new Server('127.0.0.1', 27017, {}));
exports.open = function(callback) {
  db.open(function(err, db) {
    callback(err, db);
  });
};

var Store = function Store(collectionName, map, create) {
  this.collectionName = collectionName;
  this.map = map;
  this.create = create;
};

Store.prototype.findOne = function(doc, callback) {
  var self = this;
  db.collection(this.collectionName, function(err, collection) {
    if (err) { callback(err); return; }
    collection.findOne(doc, function(err, result) {
      if (err) { callback(err); return; }
      callback(null, self.createInstance(result));
    });
  });
};

Store.prototype.idFromString = function(str) {
  return ObjectID.createFromHexString(str);
};

Store.prototype.createInstance = function(result) {
  var o = this.create(); 
  for (var key in result) {
    o[this.map[key]] = result[key];
  }
  return o;
}

module.exports.Store = Store;


//example.js
var Account = require('./account'),
    Store = require('./store');

Store.open(function(err, db) {
  Account.findById("4e5894ab50c75b3949c62c76", function(err, account){
    console.log(account);
  });
  db.closse();
});