Appending files in Node.js allows you to add new content to existing files without overwriting previous data, essential for logging, data collection, and incremental file updates. As the creator of CoreUI, a widely used open-source UI library, I’ve implemented file appending in countless Node.js applications for logging systems, data processing, and content management. From my expertise, the most effective approach is using fs.appendFile() for simple operations and fs.createWriteStream() for high-performance scenarios. This method provides efficient file writing with proper error handling and optimal performance for various use cases.