Q.236: What is event loop? - Unsatisfactory answer

[sidsinr]

Given answer:

The Event Loop is a queue of callback functions. When an async function executes, the callback function is pushed into the queue. The JavaScript engine doesn't start processing the event loop until the async function has finished executing the code. Note: It allows Node.js to perform non-blocking I/O operations even though JavaScript is single-threaded.

From what I have learned from the external sources, the event loop is not actually a queue but a mechanism that works by continuously checking the call stack to see if there are any functions waiting to be executed. If the call stack is empty, the event loop checks the callback queue for any pending events. If there are any events, the event loop will pop the first event off the queue and add it to the call stack.

The MDN docs even describe the event loop implementation similar to:

while (queue.waitForMessage()) {
  queue.processNextMessage();
}

P.S. Thank you for compiling all the questions. It's really helpful for my revision.

[sudheerj]

@sidsinr Thanks for your feedback. Can you make a PR?

[sidsinr]

#182 - PR

@sudheerj I've made a PR. Could you review it?

I've updated the answer for question 236- What is an event loop.
The original answer had a reference to Node.js, so I elaborated it.

Also, there was a tiny typo and the last code was not rendering in the markdown in question 450. I just fixed the indentation which was causing the problem.

Let me know if there is any problem, or if you want me to make any changes.

[sidsinr]

Also the last line of the answer for question "238-What is event queue" is kindof the answer to the event loop.

The event queue constantly checks whether or not the call stack is empty. Once the call stack is empty and there is a callback in the event queue, the event queue moves the callback into the call stack. If there is a callback in the microtask queue as well, it is moved first. The microtask queue has a higher priority than the event queue.

It would be better if this line is deleted, because it creates confusion.

[sudheerj]

@sidsinr PR has been merged. I will update the answer related to event queue if no one else has some suggestions or PRs. Thanks again.