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db.getConnection is not a function

I am trying to make a post request to my first app, but every time I go to make the post, it gives me this error: TypeError: db.getConnection is not a function
I have tried all of stack overflows suggestions, but I still can't seem to get it to work after messing around with the code for the last 2 days. I am a beginner so please forgive me, but here is what my code looks like...
my db.js looks like this....
var mysql = require('mysql');
var mainDb = mysql.createPool({
host : process.env.mysql_host,
user : process.env.mysql_user,
password : process.env.mysql_pwd,
database : process.env.mysql_db
});
exports.getConnection = function(callback) {
mainDb.getConnection(function(err, connection) {
if (err) {
console.error('error connecting: ' + err.stack);
return;
}
callback(err, connection);
});
};
and my register.js code looks like this...
var express = require('express');
var router = express.Router();
var db = require(__dirname, 'models/db');
var bodyParser = require('body-parser');
app.use(bodyParser.urlencoded({
extended: false
}));
app.use(bodyParser.json());
router.get('/register', function(req, res, next) {
res.render('register', { title: 'Register for a free account' });
});
router.post('/register', function(req, res) {
var input = JSON.parse(JSON.stringify(req.body));
var today = new Date();
var users = {
"username": req.body.username,
"email":req.body.email,
"password":req.body.password,
"created":today,
"modified":today
};
db.getConnection(function(err, connection) {
connection.query('INSERT INTO users SET ? ', users, function(err, result) {
connection.release();
if (err) { return console.error(err); }
});
});
res.redirect('/index');
});
module.exports = router;
I don't know if my app.js is relevant for this question, but it looks like this...
const express = require('express');
http = require('http');
path = require('path');
session = require('express-session');
app = express();
mysql = require('mysql');
bodyParser = require('body-parser');
db = require(__dirname, 'models/db')
var index = require('./routes/index');
var register = require('./routes/register');
app.use('/', index);
app.use('/', register);
var engine = require('ejs-mate');
app.engine('ejs', engine);
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'ejs');
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({extended: false}));
app.use(express.static(path.join(__dirname, 'public')));
var server = http.createServer(app);
var port = 8995;
server.listen(port);
module.exports = app;
When I start app.js I get no errors, only when I make my post request from my form, the error shows up in my browser. Please help!

At db.js you are exporting only a function. But at register.js, you are trying to use db as if it was an object.
To solve your problem, at db.js, just export an object, instead of a function:
function getConnection(callback) {
mainDb.getConnection(function(err, connection) {
if (err) {
console.error('error connecting: ' + err.stack);
return;
}
callback(err, connection);
}
module.exports = { getConnection };

You don't need use getConnection method only exports the pool, according the documentation.
https://github.com/mysqljs/mysql

Handle localization in single-page web application

I have to add a localization mechanism into an existing Node.js web application.
The application is composed of:
Node.js server
Dojo / javascript single web page (i.e. each dojox/mobile/View is shown as needed)
I've already configured i18nextify and it works fine, adding a query parameter to the initial request:
http://127.0.0.1:8000/?lng=en
My question is related about how to handle this query after the page has loaded.
Here the flow of the application:
the users load the initial page with the default url (i.e. http://127.0.0.1:8000)
after logging in, the server retrieves the pre-defined language for that user (the application should not offer the language selection to the end user)
now the new views show the desired language
A way I found:
After the client receives the language tag ('en') in the login answer - see below, it stores it in the session storage and reloads the page appending the language to the query request ('/?lng=en'). On next reload, if the application finds the existence of that variable in the session storage pass-over the login page. The logout function will remove the variable.
I'm afraid about security issue here, or out-of-sync between session storage variables and server knowledge of client's connection.
Here my code for initializing i18next on the server:
app.js
var express = require('express');
var i18next = require('i18next');
var FsBackend = require('i18next-node-fs-backend');
var middleware = require('i18next-express-middleware');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var https = require('https');
var routes = require('./routes/index');
i18next
.use(FsBackend)
.init({
lng: 'it',
saveMissing: true,
debug: true,
backend: {
loadPath: __dirname + '/locales/{{lng}}/{{ns}}.json',
addPath: __dirname + '/locales/{{lng}}/{{ns}}.missing.json'
},
preload: [ 'it' ],
nsSeparator: '#||#',
keySeparator: '#|#'
});
var app = express();
app.use(middleware.handle(i18next, {
}));
app.use('/locales', express.static('locales'));
app.post('/locales/add/:lng/:ns', middleware.missingKeyHandler(i18next));
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');
app.use(favicon(path.join(__dirname, 'public', 'favicon.ico')));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({extended: true}));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));
app.use('/', routes);
app.use(function (req, res, next) {
var err = new Error('Not Found');
err.status = 404;
next(err);
});
if (app.get('env') === 'development') {
app.use(function (err, req, res, next) {
res.status(err.status || 500);
res.render('error', { message: err.message, error: err });
});
}
app.use(function (err, req, res, next) {
res.status(err.status || 500);
res.render('error', { message: err.message, error: {} });
});
module.exports = app;
index.js
var express = require("express");
var router = express.Router();
var fs = require('fs');
router.get("/", function (req, res, next) {
res.render("index", {title: "Smart Data Collector"});
});
router.get('/i18nextify.min.js', function(req, res) {
fs.readFile(__dirname + '/../node_modules/i18nextify/i18nextify.js', 'utf-8', function(err, doc) {
res.send(doc);
});
});
router.post("/api/login", function (req, res, next) {
var header = JSON.parse(req.headers.login);
var name = header.name;
var pin = header.pin;
// myengine is a collection of utility functions
myengine.login(name, pin, function (result, sid) {
res.status(200).json({
result: result.login,
sid: sid,
name: name,
id: result.id,
lang: result.lang // here the language retrieved by the server
});
});
});
and here the client initialization:
script(src="/i18nextify.min.js")
script(src="/javascripts/dojo/dojo.js")
script(type="text/javascript").
var translation = window.i18nextify.init({
debug: true,
saveMissing: true,
namespace: 'translation',
ns: ['common', 'commonNested'],
ignoreTags: ['SCRIPT', 'h6'],
ignoreIds: ['ignoreMeId'],
ignoreClasses: ['ignoreMeClass']
});
...other js libraries follows

rethinkdb changesfeed in express with socket.io displaying [object object]

I'm using express.js, rethinkdb, thinky, socket.io. Trying to notify the index page of any changes that happens in the db. So I use rethinkdb changesfeed (and I can see the updates in console.log) but the cursor/feed is showing object object instead of the data.
When I pass the feed results to the socket.emit, it displays [object object]?
I read and implemented the code that comes from the rethinkdb blog (https://www.rethinkdb.com/blog/cats-of-instagram/) but it is not working.
Please scroll down to the bottom with socket.io header
App.js
var express = require('express');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');
var r = require('rethinkdb');
// *********** Thinky code*********************//
var changeStream = require("rethinkdb-change-stream");
var thinky = require('thinky')()
var type = thinky.type;
var r = thinky.r;
//thinky model
var User = thinky.createModel('User', {
author: type.string()
});
/*
User.changes().then(function (feed) {
feed.each(function (error, doc) {
if (error) {
console.log(error);
process.exit(1);
}
if (doc.isSaved() === false) {
console.log("The following document was deleted:");
console.log(JSON.stringify(doc));
}
else if (doc.getOldValue() == null) {
console.log("A new document was inserted:");
console.log(JSON.stringify(doc));
}
else {
console.log("A document was updated.");
console.log("Old value:");
console.log(JSON.stringify(doc.getOldValue()));
console.log("New value:");
console.log(JSON.stringify(doc));
}
});
}).error(function (error) {
console.log(error);
process.exit(1);
});
*/
//*********End Thinky Code ******************//
// Mongodb Example http://www.guru99.com/node-js-mongodb.html
var MongoClient = require('mongodb').MongoClient
var url = 'mongodb://localhost/EmployeeDB';
var routes = require('./routes/index');
var users = require('./routes/users');
var app = express();
//attach socket server to express server so it interacts with clients requests and responses
app.io = require('socket.io')();
// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');
// uncomment after placing your favicon in /public
//app.use(favicon(__dirname + '/public/favicon.ico'));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(require('stylus').middleware(path.join(__dirname, 'public')));
app.use(express.static(path.join(__dirname, 'public')));
app.use('/', routes);
app.use('/users', users);
// catch 404 and forward to error handler
app.use(function (req, res, next) {
var err = new Error('Not Found');
err.status = 404;
next(err);
});
// error handlers
// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
app.use(function (err, req, res, next) {
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: err
});
});
}
// production error handler
// no stacktraces leaked to user
app.use(function (err, req, res, next) {
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: {}
});
});
/* )))))))))))))))) socket.io Header ((((((((((((((((((( */
app.io.on('connection', function (socket) {
r.connect(host = 'localhost', port = 28015, db = 'test').then(function (conn) {
this.conn = conn;
return r.table("User").changes().run(this.conn).then(function (cursor) {
cursor.each(function (err, item) {
console.log(item);
//if (item && item.new_val)
socket.emit("message-from-server", { greeting: item });
});
})
});
// socket.emit("message-from-server", { greeting: "Say whatever here- it will show on the index page"});
});
module.exports = app;

From your code:
console.log(item);
//if (item && item.new_val)
socket.emit("message-from-server", { greeting: item });
This tells me that item is probably an object so when you pass it to the web api to add to the DOM it renders the object reference [object Object] because its expecting a string (not an object). So you can pull out the info you want from item using . syntax for objects or [<index>] syntax for arrays, or you could do something like item.toString() to attempt to turn the whole thing into a string. It really depends on the structure of item and how you are adding it to the DOM. You could do it on the client side or do it before it's emitted from your server.

Passing Mongo DB Object DB to Express Middleware

I am having problems trying to access the "DB" database object that is created when the MongoDB client module connects to my MongoDB database.
At the moment I am getting an error stating that, within data.js, 'db' is not defined. I understand why this is - the db object is not being "passed" through to the router and then subsequently through to the controller.
What is the best way to do this?
I have tried to pass the "db" object through to the router (dataRoutes.js) but I cannot figure how to make this accessible to the controller (data.js). Could someone please help?
Please note I have not included the other routes and controllers but they simply submit a Form via the POST method to /data/submit . The controller below is meant to write this form data to the MongoDB database.
Here is the relevant code:
app.js
var express = require('express');
var path = require('path')
var MongoClient = require('mongodb').MongoClient;
var bodyParser = require('body-parser');
var app = express();
var routes = require('./routes/index');
var dataRoutes = require('./routes/dataRoutes');
app.use(bodyParser.urlencoded({ extended: false }));
app.use(express.static(path.join(__dirname, 'public')));
// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'pug');
MongoClient.connect("mongodb://localhost:27017/m101", function(err, db) {
if(err) throw err;
console.log("Successfully connected to MongoDB.");
app.use('/', routes); // Use normal routes for wesbite
app.use('/data', dataRoutes);
app.get('/favicon.ico', function(req, res) {
res.send(204);
});
app.use(function(req, res, next) {
var err = new Error('Oops Page/Resource Not Found!');
err.status = 404;
next(err); //Proceed to next middleware
});
if (app.get('env') === 'development') {
app.use(function(err, req, res, next) {
// update the error responce, either with the error status
// or if that is falsey use error code 500
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: err
});
});
}
app.use(function(err, req, res, next) {
console.log('Error');
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: {}
});
});
var server = app.listen(3000, function() {
var port = server.address().port;
console.log("Express server listening on port %s.", port);
});
});
dataRoutes.js
// router
var express = require('express');
var router = express.Router();
// controller references
var ctrlsData = require('../controllers/data');
router.post('/submit', ctrlsData.submit);
module.exports = router;
data.js
var MongoClient = require('mongodb').MongoClient;
var sendJsonResponse = function(res, status, content) {
res.status(status);
res.json(content);
};
module.exports.submit = function(req, res) {
var title = req.body.title;
var year = req.body.year;
var imdb = req.body.imdb;
/*
console.log('submitted');
console.log(req.body);
sendJsonResponse(res, 201, {title,year,imdb});
*/
var title = req.body.title;
var year = req.body.year;
var imdb = req.body.imdb;
if ((title == '') || (year == '') || (imdb == '')) {
sendJsonResponse(res, 404, {
"message": "Title, Year and IMDB Reference are all required."
});
} else {
db.collection('movies').insertOne(
{ 'title': title, 'year': year, 'imdb': imdb },
function (err, r) {
if (err) {
sendJsonResponse(res, 400, err);
} else {
sendJsonResponse(res, 201, "Document inserted with _id: " + r.insertedId + {title,year,imdb});
}
}
);
}
};

Create a db variable that reference mongodb in app.js :
MongoClient.connect("mongodb://localhost:27017/m101", function(err, db) {
app.db = db;
//.....
});
In data.js, access db from req.app :
module.exports.submit = function(req, res) {
req.app.db.collection('movies').insertOne({ 'title': title, 'year': year, 'imdb': imdb },
function(err, r) {}
)
};

The accepted answer isn't quite correct. You shouldn't attach custom objects to the app object. That's what app.locals is for. Plus, the accepted answer will fail when using Typescript.
app.locals.db = db;
router.get('/foo', (req) => {
req.app.locals.db.insert('bar');
});
Sure, it's longer. But you get the assurance that future updates to ExpressJS will not interfere with your object.

I understand that the answer of #Bertrand is functional, but it is not usually recommended. The reason being that, from a software point of view, you should have a better separation in your software.
app.js
var express = require('express');
var path = require('path')
var MongoClient = require('mongodb').MongoClient;
var bodyParser = require('body-parser');
var app = express();
var routes = require('./routes/index');
var dataRoutes = require('./routes/dataRoutes');
var DB = require('./db.js');
app.use(bodyParser.urlencoded({ extended: false }));
app.use(express.static(path.join(__dirname, 'public')));
// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'pug');
DB.Init("mongodb://localhost:27017/m101")
.then(() => {
console.log("Successfully connected to MongoDB.");
app.use('/', routes); // Use normal routes for wesbite
app.use('/data', dataRoutes);
app.get('/favicon.ico', function(req, res) {
res.send(204);
});
var server = app.listen(3000, function() {
var port = server.address().port;
console.log("Express server listening on port %s.", port);
});
})
.catch((e) => {
console.log("Error initializing db");
});
db.js
var _db = null;
module.exports = {
Init: (url) => {
return new Promise((resolve, reject) => {
if (!url)
reject("You should provide a URL");
MongoClient.connect("mongodb://localhost:27017/m101", function(err, db) {
if(err) reject(err);
_db = db;
resolve(); // Or resolve(db) if you wanna return the db object
});
});
},
Submit: (req, res, next) => {
// Whatever goes. You have access to _db here, too!
}
};
in data.js
var DB = require('../db.js');
router.post('/submit', DB.submit);
Finally, even this answer can be improved as you are not usually advised to wait for the DB to connect, otherwise, you are losing the advantage of using ASync procs.
Consider something similar to here in app.js:
Promise.resolve()
.then(() => {
// Whatever DB stuff are
// DB.Init ?
})
.then(() => {
// Someone needs routing?
})
...
.catch((e) => {
console.error("Ther app failed to start");
console.error(e);
});
I understand that in the last sample, you can not instantly query DB as it may not have connected yet, but this is a server, and users are usually expected to wait for your DB to init. However, if you wanna more proof solution, consider implementing something yourself in DB.submit to wait for the connect. Or, you can also use something like mongoose.

Using MongoDB, Express, Node.Js and GridFS-stream for storing video and picture files

I am creating a single page application using JavaScript(JQuery) and need to store large video files which size exceed 16Mb. I found that need to use GridFS supporting large files. As I am the new one to MongoDB I am not sure how to use GridFS. There are some good tutorials on creating applications using Node.js, MongoDB and Express but cant find any describing how to use GridFS with MongoDB (not mongoose), Express and Node.js. I managed to put up stuff for uploading files in the BSON-document size limit of 16MB. This is what I have:
var express = require('express');
var path = require('path');
var bodyParser = require('body-parser');
var mongo = require('mongodb');
var monk = require('monk');
var Grid = require('gridfs-stream');
var db = monk('localhost:27017/elearning');
var gfs = Grid(db, mongo);
var routes = require('./routes/index');
var users = require('./routes/users');
var courses = require('./routes/courses');
var app = express();
// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));
// Make our db accessible to our router
app.use(function(req,res,next){
req.db = db;
next();
});
app.use('/', routes);
app.use('/users', users);
app.use('/courses', courses);
// catch 404 and forward to error handler
app.use(function(req, res, next) {
var err = new Error('Not Found');
err.status = 404;
next(err);
});
// error handlers
// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
app.use(function(err, req, res, next) {
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: err
});
});
}
// production error handler
// no stacktraces leaked to user
app.use(function(err, req, res, next) {
res.status(err.status || 500);
res.render('error', {
message: err.message,
error: {}
});
});
module.exports = app;
And, for example, the courses file is as the following:
var express = require('express');
var router = express.Router();
/* GET courses listing */
router.get('/courselist', function(req, res) {
var db = req.db;
var collection = db.get('courselist');
collection.find({},{},function(e,docs){
res.json(docs);
})
});
/* POST courses data */
router.post('/courselist', function(req, res) {
var db = req.db;
var collection = db.get('courselist');
collection.insert(req.body, function(err, result){
res.send(
(err === null) ? { msg: '' } : { msg: err }
);
});
});
/* Delete courses data */
router.delete('/courselist/:id', function(req, res) {
var db = req.db;
var collection = db.get('courselist');
var userToDelete = req.params.id;
collection.remove({ '_id' : userToDelete }, function(err) {
res.send((err === null) ? { msg: '' } : { msg:'error: ' + err });
});
});
module.exports = router;
I would be extremely grateful for your help, if you could tell how should I edit above files in order to utilize GridFS and be able to get, upload and delete video and picture files from my elearning database.

You can do direct uploading without using mongoose using gridfs-stream as simple as:
var express = require('express'),
mongo = require('mongodb'),
Grid = require('gridfs-stream'),
db = new mongo.Db('node-cheat-db', new mongo.Server("localhost", 27017)),
gfs = Grid(db, mongo),
app = express();
db.open(function (err) {
if (err) return handleError(err);
var gfs = Grid(db, mongo);
console.log('All set! Start uploading :)');
});
//POST http://localhost:3000/file
app.post('/file', function (req, res) {
var writeStream = gfs.createWriteStream({
filename: 'file_name_here'
});
writeStream.on('close', function (file) {
res.send(`File has been uploaded ${file._id}`);
});
req.pipe(writeStream);
});
//GET http://localhost:3000/file/[mongo_id_of_file_here]
app.get('/file/:fileId', function (req, res) {
gfs.createReadStream({
_id: req.params.fileId // or provide filename: 'file_name_here'
}).pipe(res);
});
app.listen(process.env.PORT || 3000);
for complete files and running project:
Clone node-cheat direct_upload_gridfs, run node app followed by npm install express mongodb gridfs-stream.
OR
Follow baby steps at Node-Cheat Direct Upload via GridFS README.md

Very late but I found previous answer outdated. I'm posting this because this might help newbies like me. To run it, please follow previous answers guide. All credit goes to #ZeeshanHassanMemon.
var express = require('express'),
mongoose = require('mongoose'),
Grid = require('gridfs-stream'),
app = express();
Grid.mongo = mongoose.mongo;
conn = mongoose.createConnection('mongodb://localhost/node-cheat-db');
conn.once('open', function () {
var gfs = Grid(conn.db);
app.set('gridfs', gfs);
console.log('all set');
});
//POST http://localhost:3000/file
app.post('/file', function (req, res) {
var gridfs = app.get('gridfs');
var writeStream = gridfs.createWriteStream({
filename: 'file_name_here'
});
writeStream.on('close', function (file) {
res.send(`File has been uploaded ${file._id}`);
});
req.pipe(writeStream);
});
//GET http://localhost:3000/file/[mongo_id_of_file_here]
app.get('/file/:fileId', function (req, res) {
var gridfs = app.get('gridfs');
gridfs.createReadStream({
_id: req.params.fileId // or provide filename: 'file_name_here'
}).pipe(res);
});
app.listen(process.env.PORT || 3000);