How to build a file upload service with vanilla JavaScript

The article provides a detailed guide on building a file upload service using vanilla JavaScript, without relying on third-party packages, to deepen understanding of core JavaScript concepts. It walks through setting up a Node.js server and a basic HTML frontend to read and upload files. The process involves reading file content on the frontend using the FileReader object, dividing the file into chunks to avoid server overload, and streaming these chunks to the backend server while ensuring they are uploaded in order. The guide also extends the implementation to support multiple file uploads by modifying the input and iterating over the files array. The server is designed to handle chunk reception and file storage efficiently, and the method allows for parallel chunk uploads while maintaining a stateless backend. The tutorial emphasizes understanding the underlying mechanisms in JavaScript, offering potential extensions like adding a progress bar and handling chunk upload failures.