JavaScript Interview Questions

The event loop is a fundamental part of JavaScript's runtime model, allowing the language to perform non-blocking operations by offloading tasks to the system kernel whenever possible. The event loop continuously checks the call stack to see if there's any function that needs to be run. When the call stack is empty, it processes messages from the queue. This model enables JavaScript to handle asynchronous tasks like I/O operations, network requests, and timers efficiently.

Here is an example demonstrating the event loop:

console.log('Start');

setTimeout(() => {
    console.log('Timeout');
}, 0);

console.log('End');

In this example, 'Start' is logged first, followed by 'End', and finally 'Timeout'. Even though the setTimeout is set to 0 milliseconds, it is placed in the event queue and only executed after the current call stack is empty.