How does the JavaScript event loop work?

Absolutely! The JavaScript **event loop** is a fundamental concept that helps JavaScript handle asynchronous operations, even though it’s a single-threaded language (meaning it can do one thing at a time). ### The Call Stack Think of the **call stack** as a to-do list where JavaScript keeps track of what function is currently running. When a function is called, it gets added (pushed) to the top of the stack. Once the function finishes, it’s removed (popped) from the stack. JavaScript runs code **synchronously** by default, so it executes one function at a time, following the stack order. ### Web APIs and Callback Queue When JavaScript encounters an asynchronous operation (like a `setTimeout`, a network request, or an event listener), it doesn’t block the call stack. Instead, it delegates the work to the browser’s **Web APIs** (or Node.js APIs in server-side JavaScript). For example, if you use `setTimeout`, the timer runs separately. Once the asynchronous operation completes, its callback function is placed into a **callback queue** (also called the task queue). This queue holds functions waiting to be executed. ### The Event Loop Here’s where the **event loop** comes in! Its job is to constantly check the call stack and the callback queue: - If the call stack is **empty** (no functions currently running), - The event loop takes the first callback from the callback queue and pushes it onto the call stack, - Then the function runs, and when done, it’s removed from the stack. This cycle repeats continuously, allowing JavaScript to handle asynchronous tasks without blocking the main thread. ### Summary in Simple Terms - JavaScript runs one thing at a time using the call stack. - Asynchronous tasks are handled outside the stack by browser APIs. - When those tasks finish, their callbacks go into a queue. - The event loop moves callbacks from the queue to the stack **when it’s free**. - This lets JavaScript do things like wait for timers, handle clicks, or fetch data smoothly. If you want, I can also share a simple diagram or code example to illustrate this!