How do you understand asynchrony in Node.js? What are the microtask queue and macrotask queue?

Asynchronous in Node.js is the ability to perform operations without blocking the main thread. Node.js uses an event loop that processes tasks as they become ready, allowing efficient handling of I/O.

Microtask queue and macrotask queue are two task queues with different priorities in the event loop:

• Macrotask queue (or simply task queue) contains tasks such as event handlers, timers (setTimeout, setInterval), I/O operations. After the current call stack is executed, the event loop takes a task from this queue.

• Microtask queue contains tasks that should be executed immediately after the current call stack but before the next macrotask. This includes promises (.then, .catch), process.nextTick in Node.js.

Execution order:

1. The current call stack is executed.
2. All tasks from the microtask queue are executed.
3. One task from the macrotask queue is executed.
4. The cycle repeats.

This provides a faster response to promises and other microtasks compared to macrotasks.