javascript - How to reuse mongodb connection through Promise -

i want reuse mongodb connection. 'am aware of how reuse mongodb connection in node.js want acheive same using promises , mongo driver v2

currently have connect db every request makes slow. code

"use strict" var app = require('./utils/express')(); var mongodb = require('mongodb');  var mongoclient = mongodb.mongoclient; //actually 'am connecting mongolab var url = 'mongodb://localhost/my-mongo';  app.set('port', (process.env.port || 5000));  app.listen(app.get('port'), function () {   console.log('parkme app running on port', app.get('port')); });   app.get('/location/create', function(req,res,next){   mongoclient.connect(url).then(function(db) {     return db.collection('parkme_parkinglots').find({}).toarray().then(function (docs) {       return docs;     });   }); }); 

i want like:

"use strict" var app = require('./utils/express')(); var mongodb = require('mongodb');  var mongoclient = mongodb.mongoclient; var url = 'mongodb://nidhind:1234@ds051635.mongolab.com:51635/my-mongo'; var db = mongoclient.connect(url).then(function(db) {     return db; });  app.set('port', (process.env.port || 5000));  app.listen(app.get('port'), function () {   console.log('parkme app running on port', app.get('port')); });   app.get('/location/create', function(req,res,next){   db.collection('parkme_parkinglots').find({}).toarray().then(function (docs) {     return docs;   }); }); 

you're there, there couple of changes in code made:

"use strict" var app = require('./utils/express')(); var mongodb = require('mongodb');  var mongoclient = mongodb.mongoclient; var url = 'mongodb://nidhind:1234@ds051635.mongolab.com:51635/my-mongo'; // no need call then() yet var connection = mongoclient.connect(url);  app.set('port', (process.env.port || 5000));  app.listen(app.get('port'), function() {   console.log('parkme app running on port', app.get('port')); });   app.get('/location/create', function(req, res, next) {   // connection opened once, use @   connection.then(function(db) {     db.collection('parkme_parkinglots').find({}).toarray().then(function(docs) {       return docs;     });   }); });