Node.js

Node.js is an open-source, cross-platform JavaScript runtime environment that executes JavaScript code outside of a web browser. It allows developers to use JavaScript to write command-line tools and, most commonly, for server-side scripting—running scripts server-side to produce dynamic web page content before the page is sent to the user's web browser. The key architectural feature of Node.js is its non-blocking, event-driven I/O model. In traditional server-side programming, if a request involves a long-running I/O (Input/Output) operation, like reading a file from the disk or making a database query, the server thread would block and wait for that operation to complete before it could handle any other requests. Node.js, however, uses a single-threaded event loop. When it encounters an I/O operation, it sends the operation to the system kernel and immediately moves on to handle the next request. When the I/O operation is finished, the kernel informs Node.js, which then adds the corresponding callback function to a queue to be executed. This model makes Node.js incredibly efficient and scalable, especially for I/O-heavy applications like real-time chat apps, streaming services, and API servers. It also comes with a rich ecosystem of packages managed by npm (Node Package Manager), which is the world's largest software registry.