typeerror: app.use() requires middleware function

Question

I am learning node.js with express template engine, I am following udemy course "learn node.js by building 10 projects", while following a lecture when professor run npm start localhost:3000 starts while mine pops up error indicating app.use requires middleware function I have tried matching code and its same. Please help me to resolve the error i have been stuck here for hours tried a lot of edits but its not working for me.

When I am trying to run 'npm start' following error pops up

TypeError: app.use() requires middleware functions

Here is app.js code:

var express = require('express'); var path = require('path'); var favicon = require('serve-favicon'); var logger = require('morgan'); var expressValidator = require('express-validator'); var cookieParser = require('cookie-parser'); var session = require('express-session'); var passport = require('passport'); var LocalStrategy = require('passport-local').Strategy; var bodyParser = require('body-parser'); var multer = require('multer'); var flash = require('connect-flash'); var mongo = require('mongodb'); var mongoose = require('mongoose'); var db = mongoose.connection;  var routes = require('./routes/index'); var users = require('./routes/users');  var app = express();  // view engine setup app.set('views', path.join(__dirname, 'views')); app.set('view engine', 'jade');  //Handle File Uploads app.use(multer({   dest: './uploads' }));  // 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 }));  //Handle Express Sessions app.use(session({   secret: 'secret',   saveUninitialied: true,   resave: true }));  //Passport app.use(passport.initialize()); app.use(passport.session());  //Validator app.use(expressValidator({   errorFormatter: function(param, msg, value) {     var namespace = param.split('.'),       root = namespace.shift(),       formParam = root;      while (namespace.length) {       formParam += '[' + namespace.shift() + ']';     }     return {       param: formParam,       msg: msg,       value: value     };   } }));  app.use(cookieParser()); app.use(express.static(path.join(__dirname, 'public')));  app.use(flash());  app.use(function(req, res, next) {   res.locals.messages = require('express-messages')(req, res);   next(); });  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: {}   }); });    module.exports = app; 

Here is package.json file

{   "name": "nodeauth",   "version": "1.0.0",   "private": true,   "scripts": {     "start": "node ./bin/www"   },   "dependencies": {     "body-parser": "~1.12.4",     "cookie-parser": "~1.3.5",     "debug": "~2.2.0",     "express": "~4.12.4",     "jade": "~1.9.2",     "morgan": "~1.5.3",     "serve-favicon": "~2.2.1",     "mongodb": "*",     "mongoose": "*",     "connect-flash": "*",     "express-validator": "*",     "express-session": "*",     "express-messages": "*",     "passport": "*",     "passport-local": "*",     "passport-http": "*",     "multer": "*"   } } 

Here is updated app.js (after removing multar)

var express          = require('express'),     path             = require('path'),     favicon          = require('serve-favicon'),     logger           = require('morgan'),     cookieParser     = require('cookie-parser'),     expressValidator = require('express-validator'),     session          = require('express-session'),     passport         = require('passport'),     LocalStrategy    = require('passport-local').Strategy,     bodyParser       = require('body-parser'),     flash            = require('connect-flash'),     mongo            = require('mongodb'),     mongoose         = require('mongoose'),      db = mongoose.connection,      routes = require('./routes/index'),     users  = require('./routes/users'),      app = express();  // view engine setup app.set('views', path.join(__dirname, 'views')); app.set('view engine', 'jade');  // handle file uploads  //multer delted   // 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 }));  // handle express sessions app.use(session({   secret: 'keyboard cat',   resave: true,   saveUninitialized: true }));  // passport app.use(passport.initialize()); app.use(passport.session());  // validator app.use(expressValidator({   errorFormatter: function(param, msg, value) {     var namespace = param.split('.'),         root      = namespace.shift(),         formParam = root;      while(namespace.length) {       formParam += '[' + namespace.shift() + ']';     }      return {       param: formParam,       msg  : msg,       value: value     };   } }));  app.use(cookieParser()); app.use(express.static(path.join(__dirname, 'public')));  // flash app.use(flash());  // express messages app.use(function(req, res, next) {   res.locals.messages = require('express-messages')(req, res);   next(); });  app.get('*', function(req, res, next) {   res.locals.user = req.user || null;   next(); });  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: {}   }); });   //Express server var http = require('http'); var server = http.createServer(app);  app.get('/', function(req, res) {     res.send("Hello World!"); });  server.listen(3000, 'localhost'); server.on('listening', function() {     console.log('Express server started on port %s at %s', server.address().port, server.address().address); });  module.exports = app; 

Thank You

Answer 1

It worked in this way. delete this line,

app.use(multer({ dest: './uploads' })); 

and use it as,

var multer = require('multer'); var upload = multer({ dest: './uploads' }); 

I'm too following the same course

Answer 2

Change:

//Handle File Uploads app.use(multer({   dest: './uploads' })); 

For something like:

app.use(multer({dest:'./uploads/'}).single('singleInputFileName')); 

or

app.use(multer({dest:'./uploads/'}).array('multiInputFileName')); 

And be aware to have something like:

<form action="/postPhotos" enctype="multipart/form-data">     <input type="file" name="singleInputFileName">     <input type="submit" value="Upload photo"> </form> 

for the first case, or:

<form action="/postPhotos" enctype="multipart/form-data">     <input type="file" name="multiInputFileName" multiple>     <input type="submit" value="Upload photo"> </form> 

For the second one, in your html.