type error: app.use() requires middleware

Question

I can not figure out why I get this error.

When I try to run node filename.js, I got a type error on the console:

app.use() requires middleware functions

I expect the result is:

Working on port 3000

Below is my code:

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

app.use(function (req, res, next) {
  res.setHeader('Access-Control-Allow-Origin', 'http://valor-software.github.io');
  res.setHeader('Access-Control-Allow-Methods', 'POST');
  res.setHeader('Access-Control-Allow-Headers', 'X-Requested-With,content-type');
  res.setHeader('Access-Control-Allow-Credentials', true);
  next();
});

app.use(multer({
  dest: DIR,
  rename: function (fieldname, filename) {
    return filename + Date.now();
  },
  onFileUploadStart: function (file) {
    console.log(file.originalname + ' is starting ...');
  },
  onFileUploadComplete: function (file) {
    console.log(file.fieldname + ' uploaded to  ' + file.path);
  }
}));

app.get('/api', function (req, res) {
  res.end('file catcher example');
});

app.post('/api', function (req, res) {
  upload(req, res, function (err) {
    if (err) {
      return res.end(err.toString());
    }
    res.end('File is uploaded');
  });
});

var PORT = process.env.PORT || 3000;

app.listen(PORT, function () {
  console.log('Working on port ' + PORT);
});

Answer 1

According to the document of multer on npm. You can not pass multer object as an argument directly. You should pass them by calling member functions, such as single(), field(), array().

For example:

upload = multer({
  dest: DIR,
  rename: function (fieldname, filename) {
    return filename + Date.now();
  },
  onFileUploadStart: function (file) {
    console.log(file.originalname + ' is starting ...');
  },
  onFileUploadComplete: function (file) {
    console.log(file.fieldname + ' uploaded to  ' + file.path);
  }
})

app.use(upload.single(...));
app.use(upload.array(...));
app.use(upload.fields(...));
app.use(upload.any());