Multer - get underlying file's content during fileFilter

Question

I'm trying to make sure the uploaded file is an image, while using multer to handle the file upload.

The fileFilter function takes the form of the following:

  var fileType = require('file-type');

  fileFilter: function(req, file, cb){
    // Check filetype based on file content
    var filetype = fileType(// File buffer here);
    // Callback - file OK
    cb(null, true)
  }

The problem is file only contains the following:

  { fieldname: 'photo',
  originalname: 'photo.png',
  encoding: '7bit',
  mimetype: 'image/png' }

Is there a way to actually get the file's content (Buffer) in the fileFilter function so that I can inspect the file's content to determine its type?

edit: If this can be done using busboy (the module multer uses), I'd be open to a solution that involves that.

Seppuku

Yes, that's possible using the MemoryStorage rather than the DiskStorage from Multer. See the docs: github.com/expressjs/multer#memorystorage – Gnosticism

I've had a look at that, my only concern is that it might be similar to the memory-store (session store), as in - not production ready and doesn't scale well. My understanding is that it's used as more of a development tool that something widely used. – Seppuku

Do you recall if you've found a solution for this issue? – Knurl

Same problem here – Sycosis

I wanted to achieve exactly the same but unfortunately I couldn't find a clean way of doing it in 1.x, but should be possible with 2.x as it provides a stream based API - github.com/expressjs/multer/issues/723 It is still in alpha though. – Throughout