multer callbacks not working ?

It seems the usage has been changed over time. Currently, multer constructor only accepts following options (https://www.npmjs.com/package/multer#multer-opts):

• dest or storage - Where to store the files
• fileFilter - Function to control which files are accepted
• limits - Limits of the uploaded data

So, for example the renaming is to be solved by configuring appropriate storage (https://www.npmjs.com/package/multer#storage).

var storage = multer.diskStorage({
  destination: function (req, file, cb) {
    cb(null, '/tmp/my-uploads'); // Absolute path. Folder must exist, will not be created for you.
  },
  filename: function (req, file, cb) {
    cb(null, file.fieldname + '-' + Date.now());
  }
})

var upload = multer({ storage: storage });

app.post('/profile', upload.single('fieldname'), function (req, res, next) {
    // req.body contains the text fields 
});

The fieldname must match the field name in the request body. That is, in case of HTML form post, the form upload element input name.

Also have a look for other middleware functions like array and fields - https://www.npmjs.com/package/multer#single-fieldname which provide a a little different functionality.

Also you may be interested in the limits (https://www.npmjs.com/package/multer#limits) and file filter (https://www.npmjs.com/package/multer#filefilter)

And also - source is the single source of truth - have a peek!(https://github.com/expressjs/multer/blob/master/index.js)