The uploader behaviour for Dropzone changed from previous versions, making the links to sample code in the Dropzone documentation outdated ( I only discovered the change after updating to a new version of a site template that I was using - and seeing that my previous working code stopped working… )

The following works with the following (fairly current) versions : Dropzone v4.3.0, Express v4.13.4

In the GUI

<link href="/t/css/plugins/dropzone/dropzone.css" rel="stylesheet"/>
<form id="my-awesome-dropzone" action="" method="post" enctype="multipart/form-data" class="dropzone">
<div class="fallback">
<input name="source_file[]" type="file" multiple="multiple"/>
<div class="form-group pull-right">
<button id="batch-upload" type="submit" class="btn btn-danger">Upload Now! </button>
<script src="/t/js/plugins/dropzone/dropzone.js"></script>
$(document).ready(function() {

Dropzone.options.myAwesomeDropzone = {
autoProcessQueue: false,
//paramName:'source_file', // Name used to transfer the file(s) (will have '[i=0,1,2,3,4...]' appended)
paramName: function(n) { return 'source_file[]';}, // Don't enumerate the transfers
uploadMultiple: true,
parallelUploads: 4, // default is 2
//maxFilesize: 2, // MB

init: function() {
var myDropzone = this;
this.on("completemultiple", function(files, response) { // was queuecomplete

// Now reload page...
location.reload(true); // true => force server reload

this.on("addedfile", function() {
console.log("Added File! - show the upload button");

$('#batch-upload').click( function(e) {
console.log("Clicked on upload button"); // ,






On the Express server

var express = require('express');
var upload_files = require('multer')();

// .. regular set-up for 'app' ..'/batch/upload', upload_files.array('source_file[]'), process_upload);

var Promise = require('bluebird');
var fs = Promise.promisifyAll(require('fs'));
var path = require('path');
var sanitize = require("sanitize-filename");

function process_upload(req, res) {
if(req.files) {
console.log("req.files.length = ", req.files.length);

var upload_dir='uploads'; //somewhere relevant

.each(function(file_incoming, idx) {
console.log(" Writing POSTed data :", file_incoming.originalname);
var sanitized_filename = sanitize(file_incoming.originalname);
var file_to_save = path.join( upload_dir, sanitized_filename );

return fs
.writeFileAsync(file_to_save, file_incoming.buffer)
// .catch() code not included for clarity : Clearly you'll need to do some error checking...
.then( _ => {
console.log("Added files : Success");
return res.sendStatus(200);



Martin Andrews

{Finance, Software, AI} entrepreneur, living in Singapore with my family.

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