In JavaScript, the event loop is a crucial aspect of how asynchronous code execution is managed. To better comprehend the event loop and its functionality, it’s important to familiarize yourself with some key terms and concepts. Let’s dive in!

1. Call Stack

The call stack is a data structure used by JavaScript to keep track of function calls. Whenever a function is invoked, it’s added to the top of the call stack. As functions complete their execution, they are removed from the stack. The call stack operates in a Last-In-First-Out (LIFO) manner.

2. Web APIs

Web APIs are provided by web browsers and offer functionalities to interact with web resources. These APIs include features such as timers, DOM manipulation, AJAX, and more. When using a web API, the function associated with it is executed asynchronously.

3. Callback Queue

The callback queue is a queue (a data structure that operates on a First-In-First-Out (FIFO) principle) that holds callback functions. When an asynchronous task completes, the associated callback function is placed in the callback queue.

4. Event Loop

The event loop is JavaScript’s mechanism for handling asynchronous operations. It constantly checks the call stack and the callback queue. If the call stack is empty, the event loop takes the first callback function from the queue and pushes it onto the call stack to be executed.

5. Microtask Queue

Microtasks are tasks with higher priority than regular callbacks. The microtask queue holds microtasks, such as promises and mutation observers. These are executed when the call stack becomes empty, but before regular callbacks are processed.

Understanding these key terms and concepts will greatly enhance your understanding of how the JavaScript event loop operates and how asynchronous code execution is managed.

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