The event loop is Node.js's ingenious solution for achieving non-blocking I/O operations within a single-threaded environment. Operating through a series of phases, it manages tasks efficiently, ensuring smooth execution even when handling asynchronous operations like I/O tasks and timers. At its core, the event loop orchestrates these tasks by maintaining an event queue. This queue serves as a repository for various events such as I/O operations, timers, and other asynchronous tasks, awaiting their turn for processing. In Node.js, the event loop comprises six primary phases: 1. Timers: Scheduled timer callbacks are processed. 2. I/O Callbacks: Callbacks from I/O operations are handled. 3. Preparation/Idle Phase: Internal operations are performed while waiting for I/O events. 4. I/O Polling: Pending I/O operations are processed. 5. setImmediate() Callbacks Execution: Immediate callbacks are executed. 6. Close Events Callbacks: Callbacks for closed connections or resources are processed. To understand its functioning, consider the following code execution: Initially, the main thread executes the "Program start" and "Program end" code. As the event loop begins, it checks the timer phase, finding no tasks. Moving to the next phase, it processes the completed file read operation, executing the corresponding callback. Subsequently, it schedules the setTimeout callback and queues setImmediate and nextTick tasks accordingly. Upon completing the current phase, it prioritizes the execution of microtasks, such as promises or nextTick callbacks. Following this, it executes setImmediate tasks, then proceeds to the close event phase, handling any relevant callbacks. Upon completion, it revisits the timer phase, executing any scheduled timer tasks, such as setTimeout. Finally, the event loop exits gracefully. For a visual representation of the event loop in action, visit: http://latentflip.com/loupe/
The event loop is Node.js's ingenious solution for achieving non-blocking I/O operations within a single-threaded environment. Operating through a series of phases, it manages tasks efficiently, ensuring smooth execution even when handling asynchronous operations like I/O tasks and timers. At its core, the event loop orchestrates these tasks by maintaining an event queue. This queue serves as a repository for various events such as I/O operations, timers, and other asynchronous tasks, awaiting their turn for processing. In Node.js, the event loop comprises six primary phases: 1. Timers: Scheduled timer callbacks are processed. 2. I/O Callbacks: Callbacks from I/O operations are handled. 3. Preparation/Idle Phase: Internal operations are performed while waiting for I/O events. 4. I/O Polling: Pending I/O operations are processed. 5. setImmediate() Callbacks Execution: Immediate callbacks are executed. 6. Close Events Callbacks: Callbacks for closed connections or resources are processed. To understand its functioning, consider the following code execution: Initially, the main thread executes the "Program start" and "Program end" code. As the event loop begins, it checks the timer phase, finding no tasks. Moving to the next phase, it processes the completed file read operation, executing the corresponding callback. Subsequently, it schedules the setTimeout callback and queues setImmediate and nextTick tasks accordingly. Upon completing the current phase, it prioritizes the execution of microtasks, such as promises or nextTick callbacks. Following this, it executes setImmediate tasks, then proceeds to the close event phase, handling any relevant callbacks. Upon completion, it revisits the timer phase, executing any scheduled timer tasks, such as setTimeout. Finally, the event loop exits gracefully. For a visual representation of the event loop in action, visit: http://latentflip.com/loupe/