What is Event loop in JS (javascript)

In JavaScript, the event loop is an essential idea that helps us do multiple things at once, without waiting for each task to finish before starting the next one. It's like having a super assistant that manages our tasks efficiently.

With the event loop, we can work on some tasks while others are happening in the background. This allows us to do things asynchronously, meaning we don't have to pause everything when one task takes longer.

Imagine you have several chores to do, like cooking, cleaning, and reading a book. Instead of doing them one after the other, the event loop lets you cook something, then pause it to do some cleaning, and later continue cooking from where you left off. It's like multitasking!

The event loop is a part of JavaScript that ensures everything runs smoothly. It takes care of managing the order in which tasks are done, handling different events like clicking a button, and making sure that special functions (callbacks) are called at the right time.

Thanks to the event loop, JavaScript can handle complex tasks efficiently, making web applications work smoothly and respond to users quickly.

Here's how the event loop works:

Call Stack: When your JavaScript code runs, it starts by executing the statements one by one, forming a stack of function calls. The call stack is like a stack of dishes, where the top dish is the currently executing function.

Web APIs: JavaScript has access to various Web APIs provided by the browser, such as setTimeout, fetch, and more. When you use these APIs for asynchronous tasks, like setting a timer with setTimeout, these tasks are moved to the background to be handled by the browser.

Callback Queue: Once an asynchronous task is completed (e.g., the timer set by setTimeout is finished or an API request is resolved), its callback function is placed in a queue known as the "callback queue."

Event Loop: The event loop constantly monitors the call stack and checks if it is empty. If the call stack is empty, it looks at the callback queue for pending callbacks.

Dequeuing Callbacks: If there are any pending callbacks in the callback queue, the event loop takes the first one and moves it to the call stack, ready to be executed. The callback is then processed and removed from the queue.

Execution and Repeat: The callback function is executed, and if there are nested functions inside, they are executed one after the other. Once the call stack becomes empty again, the event loop repeats the process, checking for more pending callbacks in the callback queue.

By using the event loop, JavaScript can handle multiple tasks concurrently, making it suitable for tasks that require waiting for responses, such as API calls or waiting for user interactions. It ensures that the browser remains responsive and doesn't get stuck on time-consuming operations, enhancing the user experience in web applications.