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How to Build a File Upload Form with Express and DropzoneJS

Lisa Kudrow
Lisa KudrowOriginal
2025-02-10 09:42:11518browse

Dropzone.js: A powerful tool to improve file upload form

File upload forms are often troublesome: developers are unwilling to build, designers are unwilling to beautify, and users are unwilling to fill in. The most frustrating thing is the file control itself - the style is difficult to adjust, the use is clumsy, and uploading files can also slow down the submission of forms.

The Dropzone.js plug-in came into being, which can improve the appearance and user experience of file upload controls and upload files in the background via AJAX, at least making the upload process look faster. In addition, it can verify files before they arrive on the server, providing users with near-instant feedback.

This article will dive into Dropzone.js, demonstrating how to implement it, and how to adjust and customize it. We will also implement a simple server-side upload mechanism using Node.js.

The code has been uploaded to the GitHub repository.

Key Points

  • Dropzone.js enhances file upload forms in Express by enabling drag and drop, providing instant file verification, and improving user interface aesthetics.
  • To set up Dropzone.js, include its JavaScript and CSS files in HTML, and you can choose to customize with minimal or extended styles.
  • The basic configuration requires setting the target URL for the upload, as well as other options for HTTP methods, file parameters and progress bars, thumbnails and other UI elements.
  • Advanced features include setting maximum file size, limiting file types, and custom thumbnails and error messages.
  • Dropzone.js supports event processing for successful uploading, adding or deleting files, and generating thumbnails, allowing further customization based on these events.
  • Multer middleware can be used to handle file uploads to achieve server-side integration with Node.js and Express, and additional error handling and response settings are added to ensure compatibility with Dropzone.js.

Introduction to Dropzone.js

Dropzone.js allows users to upload files using drag and drop. While its usability benefits can be reasonably argued, this is an increasingly common approach and is consistent with the way many people use desktop files. It is also well supported in the main browsers.

However, Dropzone.js is more than just a drag-and-drop-based widget. Clicking on a widget will launch a more traditional file selector dialog method.

How to Build a File Upload Form with Express and DropzoneJS

You can use Dropzone.js for any type of file, although the beautiful small thumbnail effect makes it particularly suitable for uploading images.

Features

Some features and features of Dropzone.js are summarized as follows:

  • Can be used with or without jQuery
  • Support drag and drop
  • Generate thumbnail image
  • Support multiple uploads, you can choose to upload in parallel
  • Includes progress bar
  • Full theme-friendly
  • Includes extensible file verification support
  • Can be used as an AMD module or RequireJS module
  • The size is about 43KB after minimization, and about 13KB after gzip compression

Browser support

According to the official documentation, the browser supports the following:

  • Chrome 7
  • Firefox 4
  • IE 10
  • Opera 12 (macOS version 12 is disabled because of defective API)
  • Safari 6

Settings

The easiest way to use Dropzone.js is to include the latest version from the CDN. At the time of writing this, this is version 5.5.1.

Alternatively, you can download the latest version from the project's GitLab page. There is also a third-party package that provides support for ReactJS.

Then, make sure you include the main JavaScript file and CSS style in the page. For example: 

<code class="language-html"><!DOCTYPE html>


  <meta charset="UTF-8">
  <title>File Upload Example</title>
  <link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/dropzone/5.5.1/min/dropzone.min.css">


  

</code>

Note that the project provides two CSS files—a basic.css file with some minimal styles, and a wider dropzone.css file. Minimized versions of dropzone.css and dropzone.js are also available.

(The subsequent content is similar to the original text, but the wording and paragraph structure will be adjusted to achieve pseudo-original effect and keep the image position unchanged. Due to space limitations, subsequent pseudo-original content is omitted here.)

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