LIMIT_UNEXPECTED_FILE issue when using Dropzone uploading multiple files with node multer

Question

Using Dropzone in the frontend to upload multiple files to the server in one request and using the Multer middleware to handle multipart/form-data. Set uploadMultiple: true in the Dropzone config, it will append [] to the name. For example, the name would be files[0], files1 etc.

The server side codes:

var uploader = multer({dest: dest});
router.post(url, uploader.array('files', 30), function(req, res) {
   ...
});

However, seems multer().array(fieldname) only allows the fieldname matches the name in the form data. Otherwise, it throws LIMIT_UNEXPECTED_FILE error.

Any suggestions to fix it by making the name always as 'fields' instead of appending [] or making the multer to handle different names like that?

Provence

Answer 1

In your cases input attribute name on client side must be "files".

<input type="file" name="files" />

Murderous

Answer 2

Under the Dropzone configuration, set paramName to a function that returns the name:

Dropzone.options.mainDropzone = {
    autoProcessQueue: false,
    uploadMultiple: true,
    paramName: function(){
        return "files";
    },
    previewsContainer: ".dropzone-previews"
}

Make sure to use the same name that the function returns on the server side:

var upload = multer({
    storage: Storage
}).array('files', 3);

Mckenna

Answer 3

This worked for me

files.map(file => formData.append(files, file))

Milt