Home/ Questions/How can I handle - app.use() requires a middleware function?
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Evan Garcia
  • 14
Asked: 2022-05-18T18:31:06+00:00 In:

How can I handle – app.use() requires a middleware function?

  • 14

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Here is the program I run:

var express= require('express');
 var bodyParser= require('body-parser');
 var morgan = require('morgan');
 var config=require('./config');
 var app= express();
 var mongoose=require('mongoose');
 //var User=require('./database/user')
 mongoose.connect('mongodb://localhost:27017/db',function(err){
  if(err){
  console.log(err);
  }
  else{
  console.log("connected!");
  }
 });
 
 app.use(bodyParser.urlencoded({extended: true })); //if false then parse only strings
 app.use(bodyParser.json());
 app.use(morgan('dev'));//log all the requests to the console
 var api=require('./app/routes/api')(app,express);
 app.use('/api',api);
 app.get('*',function(req,res){
  res.sendFile(__dirname + '/public/views/index.html');
 }); // * means any route
 
 app.listen(config.port,function(err){
  if(err){enter code here
  console.log(err);
  }
  else{
  console.log("The server is running");
  }
 });
 module.exports = router;
var User = require('../models/user');
 var Event = require('../models/event');
 var config = require('../../config');
 var secret = config.secretKey;
 
 module.exports = function (app, express) {
  var api = express.Router();
  app.use()
 
  api.post('/signup', function (req, res) {
  var user = new User({
  name: req.body.name,
  username: req.body.username,
  password: req.body.password
  });
  user.save(function (err) {
  if (err) {
  res.send(err);
  return;
  }
  res.json({
  message: 'User created!'
  });
  });
 
  });
 
  api.get('/users', function (req, res) {
  User.find({}, function (err, users) {
  if (err) {
  res.send(err);
  return;
  }
  res.json(users);
  });
  });
 
  api.post('/eventfeed', function (req, res) {
  var event = new Event({
  name: req.body.name,
  location: req.body.location,
  description: req.body.description,
  price: req.body.price,
  rating: req.body.rating
  });
 
  event.save(function (err) {
  if (err) {
  res.send(err);
  return;
  }
  res.json({
  message: 'Event created!'
  });
  });
  });
 
  // utility function for sorting an array by a key in alpha order
  api.get('/sortby_price', function (err) {
  if (err) return err;
  // utility function for sorting an array by a key in parsed numeric order
  else {
  function sortArrayNum(arr, key) {
  arr.sort(function (a, b) {
  return parseInt(a[key], 10) - parseInt(b[key], 10);
  });
  }
 
  var dicts = EventSchema.saved;
  for (var i = 0; i < dicts.length; i++) {
  var terms = dicts[i].terms;
  sortArrayNum(terms, "price");
  }
  }
  return api;
  });
 }

After I run, it returns an error:

TypeError: app.use() requires middleware functions
  at EventEmitter.use (c:\Users\MY APY\WebstormProjects\Main\node_modules\express\lib\application.js:209:11)
  at module.exports (c:\Users\MY LAPY\WebstormProjects\Main\app\routes\api.js:10:9)
  at Object. (c:\Users\MY LAPY\WebstormProjects\Main\server.js:20:36)
  at Module._compile (module.js:460:26)
  at Object.Module._extensions..js (module.js:478:10)
  at Module.load (module.js:355:32)
  at Function.Module._load (module.js:310:12)
  at Function.Module.runMain (module.js:501:10)
  at startup (node.js:129:16)
  at node.js:814:3

Does anyone have any suggestions for the problem below: app.use() requires a middleware function in the javascript – How to correct it?

requires a middleware function
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2 Answers

  1. Best Answer
    Expert

    The cause:

    You have got this error because in your api.js the line of number 10 is not correct:

    app.use()

    A function with 3 parameters is required for app.use:

    // a middleware which has no mount path; gets performed for each requirement to the app
app.use(function (req, res, next) {
console.log('Time:', Date.now());
next();
});

    Solution:

    You can do as the following in the case you want to use this middleware by only few chosen paths:

    // a middleware which is put on /user/:id; will be executed for any types of HTTP requirement to /user/:id
app.use('/user/:id', function (req, res, next) {
console.log('Request Type:', req.method);
next();
});

// a path and the handle function of it (middleware system) which handles GET requirements to /user/:id
app.get('/user/:id', function (req, res, next) {
res.send('USER');
});
    • 0

  2. This was the problem I faced when I left. 

    module.exports = router;

    In my Routes.js. We need to export all routes.

    In my server.js I had 

    var mainRoutes = require('./Routes.js')
app.use(mainRoutes)

    Check your ‘app/routes/api” file to verify that it is exportable.

    • 7

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