In Node.js, all I/O operations are performed asynchronously, which means that they don’t block the execution of the main thread. Instead, these I/O operations are registered with the event loop, and the event loop will call the callback function when the I/O operation is complete
This allows the program to continue executing other code while waiting for the I/O operation to complete.
The event loop in Node.js consists of several phases, including the
timers phase, the
pending callbacks phase, the
idle, prepare phase, and the
poll phase. In each phase, the event loop will process a different set of tasks. For example, in the
timers phase, it will process timers that have expired, and in the
poll phase, it will process I/O events.
It’s important to note that the event loop is a single-threaded loop, which means that only one task can be processed at a time. However, due to the non-blocking nature of Node.js, the event loop can efficiently handle multiple I/O operations in parallel, which gives the illusion of multithreading.