typeerror: app.use() requires middleware function

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

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

Change:

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

For something like:

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

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.

AbdulMomen عبدالمؤمن

This worked with me:

app.use(multer({
  dest: path.join(__dirname, 'public/upload/temp')
}).any());

I was also doing that course & ran into the same problem. I resolved the error by following the Multer usage instructions from their github: https://github.com/expressjs/multer

Here is the code from their README:

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

& here is the code I used to overcome the error while doing that tutorial:

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

Hope it helps :)

you can simply use :

app.set(multer({dest: "./uploads"}));

it works for me too.

change only this line

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

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

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

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

worked for me.

来源：https://stackoverflow.com/questions/31656178/typeerror-app-use-requires-middleware-function

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