Database Singleton Object - database.js is used throughout the app to access the db object. Using mongodb native drivers the db object contains a pool of connections that are used to make requests to the db. To use this singleton object simply require it and either call getDB() or setDB(). The idea is to use setDB in app.js just after we connect…

database.js

/**
Database Singleton Object

database.js is used throughout the app to access the db object. Using mongodb
native drivers the db object contains a pool of connections that are used to
make requests to the db. To use this singleton object simply require it and
either call getDB() or setDB(). The idea is to use setDB in app.js just
after we connect to the db and receive the db object, then in any other file we
need the db require and call getDB
**/

var mongodb = require('mongodb');

var singleton = (function() {

  var instance; //Singleton Instance

  function init() {

    var _db; //Instance db object (private)
    
    //Other private variables and function can be declared here

    return {

      //Gets the instance's db object
      getDB: function() {
        return _db;
      },

      //Sets the instance's db object
      setDB: function(db) {
        _db = db;
      }
      
      //Other public variables and methods can be declared here
    };

  }

  return {
    //getInstance returns the singleton instance or creates a new one if
    //not present
    getInstance: function() {
      if (!instance) {
        instance = init();
      }

      return instance;
    }
  };

})();

module.exports = singleton.getInstance();