The answer
Timers (setTimeout), pending callbacks (deferred I/O), idle/prepare (internal), poll (new I/O events), check (setImmediate), and close callbacks. Each processes specific callback types in order through each tick of the loop.
Node.js Event Loop Interview Questions With Answers
What are the event loop phases?
More FAQs in Node.js Event Loop Interview Questions With Answers
A single-threaded loop that processes callbacks from completed async operations through phases: timers, pending, poll, check, close. It makes Node.js non-blocking by handling I/O asynchronously through libuv while processing one callback at a time.
setTimeout runs in the timers phase after a delay. setImmediate runs in the check phase right after poll. On the next tick, setImmediate usually runs before setTimeout(0) when there are no pending timers.
A Node.js-specific function that schedules a callback to run before the next event loop phase, even before promise microtasks. It is the most urgent scheduling mechanism but can starve the loop if overused, so use it sparingly.
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