The Node.js Event Loop Explained

Short summary

Node.js runs JavaScript on a single thread but achieves scalability through an event loop that manages asynchronous operations. I/O operations are delegated to the OS; when complete, their callbacks are queued and executed only when the call stack empties. The event loop operates in distinct phases for timers and I/O, which is why blocking synchronous code can delay all pending operations.

• •Event loop manages async operations by checking task queues when the call stack is empty
• •I/O operations are handed to OS/libuv while callbacks wait in queues to execute
• •Timer and I/O callbacks are processed in distinct phases; blocking synchronous code delays both

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