In Node.js, what is the primary purpose of the event loop, and how does it enable non-blocking I/O operations?

The primary purpose of the event loop in Node.js is to manage asynchronous operations in a single-threaded environment, enabling Node.js to handle multiple concurrent requests efficiently. It's the core mechanism that allows Node.js to perform non-blocking I/O (Input/Output) operations. The event loop continuously monitors the call stack and the task queue. The *call stackis where JavaScript code is executed, and the *task queueis where asynchronous operations (like reading from a file, making a network request, or setting a timer) are placed after they complete. When an asynchronous operation is initiated, instead of waiting for it to complete, Node.js registers a callback function and immediately continues executing the rest of the code. The asynchronous operation is handled by the operating system's kernel (e.g., libuv), which is more efficient at handling these tasks. Once the asynchronous operation is finished, the kernel places the corresponding callback function in the task queue. The event loop continuously checks if the call stack is empty. If it is, the event loop takes the first callback function from the task queue and pushes it onto the call stack, where it is then executed. This process repeats continuously, allowing Node.js to handle many concurrent operations without blocking the main thread. Because of the event loop, Node.js can start a file read operation, for example, and immediately begin processing other requests. When the file read operation is complete, its callback function is added to the task queue and executed when the call stack is empty. This non-blocking behavior is crucial for building highly scalable and performant network applications.