index.js
function getConnection(connectionString) {
      return new Promise(function(resolve, reject) {
        // If connectionString is null or undefined, return an error.
        if (_.isEmpty(connectionString)) {
          return reject('getConnection must be called with a mongo connection string');
        }

        // Check if a connection already exists for the provided connectionString.
        var pool = _.findWhere(connections, { connectionString: connectionString });

        // If a connection pool was found, resolve the promise with it.
        if (pool) {
          return resolve(pool.db);
        }

        // If the connection pool has not been instantiated,
        // instantiate it and return the connection.
        MongoClient.connect(connectionString, function(err, database) {
          if (err) {
            return reject(err);
          }

          // Store the connection in the connections array.
          connections.push({
            connectionString: connectionString,
            db: database
          });

          return resolve(database);
        });
      });
    }
function getConnection(connectionString) {
      return new Promise(function(resolve, reject) {
        // If connectionString is null or undefined, return an error.
        if (_.isEmpty(connectionString)) {
          return reject('getConnection must be called with a mongo connection string');
        }

        // Check if a connection already exists for the provided connectionString.
        var pool = _.findWhere(connections, { connectionString: connectionString });

        // If a connection pool was found, resolve the promise with it.
        if (pool) {
          return resolve(pool.db);
        }

        // If the connection pool has not been instantiated,
        // instantiate it and return the connection.
        MongoClient.connect(connectionString, function(err, database) {
          if (err) {
            return reject(err);
          }

          // Store the connection in the connections array.
          connections.push({
            connectionString: connectionString,
            db: database
          });

          return resolve(database);
        });
      });
    }
function getConnection ( connectionString ) { return new Promise ( function ( resolve , reject ) { // If connectionString is null or undefined, return an error. if ( _ . isEmpty ( connectionString ) ) { return reject ( 'getConnection must be called with a mongo connection string' ) ; } // Check if a connection already exists for the provided connectionString. var pool = _ . findWhere ( connections , { connectionString : connectionString } ) ; // If a connection pool was found, resolve the promise with it. if ( pool ) { return resolve ( pool . db ) ; } // If the connection pool has not been instantiated, // instantiate it and return the connection. MongoClient . connect ( connectionString , function ( err , database ) { if ( err ) { return reject ( err ) ; } // Store the connection in the connections array. connections . push ( { connectionString : connectionString , db : database } ) ; return resolve ( database ) ; } ) ; } ) ; }
Gets a Mongo connection from the pool.

If the connection pool has not been instantiated yet, it is first
instantiated and a connection is returned.

@returns {Promise|Db} - A promise object that resolves to a Mongo db object.
Gets a Mongo connection from the pool .