Understanding libuv and event loop

The event loop in LIBUV operates in four major phases:

1 Timers Phase: In this phase, all callbacks that were set using setTimeout or setInterval are executed. These timers are checked, and if their time has expired, their corresponding callbacks are added to the callback queue for execution.

2 Poll Phase: After timers, the event loop enters the Poll phase, which is crucial because it handles I/O callbacks. For instance, when you perform a file read operation using fs.readFile , the callback associated with this I/O operation will be executed in this phase. The Poll phase is responsible for handling all I/Orelated tasks, making it one of the most important phases in the event loop.

3 Check Phase: Next is the Check phase, where callbacks scheduled by the setImmediate function are executed. This utility API allows you to execute callbacks immediately after the Poll phase, giving you more control over the order of operations.

4 Close Callbacks Phase: Finally, in the Close Callbacks phase, any callbacks associated with closing operations, such as socket closures, are handled. This phase is typically used for cleanup tasks, ensuring that resources are properly released.

• Event Loop Cycle with process.nextTick() and Promises

One More Important Note

When the event loop is empty and there are no more tasks to execute, it enters the poll phase and essentially waits for incoming events