Tell me about the Event Loop: what it is, how it works.

Event Loop is a mechanism in JavaScript and other single-threaded environments that allows asynchronous operations to be processed without blocking the main thread.

How it works:

1. There is a call stack where functions are placed for execution.
2. Asynchronous operations (like timers, network requests) send their callbacks to the task queue after completion.
3. The Event Loop constantly checks if the call stack is empty. If it is, it takes the first task from the queue and pushes it onto the stack for execution.

Thus, even with asynchronous operations, the code executes sequentially without blocking the UI or other processes.

Example:

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

The output will be:

Start
End
Timeout

Because the callback of setTimeout goes into the task queue and executes after the call stack is cleared.