Learn how to build a Node.js file upload API with Express in this comprehensive backend web development tutorial. Create a simple REST API with an upload endpoint that allows uploading files of any chosen type. Follow along to set up a basic server, create an HTML file upload form, implement JavaScript for file submission, and develop custom middleware for file payload validation, size limiting, and extension filtering. Explore the process of saving uploaded files to the server and thoroughly test the entire file upload process. Gain practical experience in handling file uploads in Node.js applications using Express and the express-fileupload package.