Node.js Q & A


What is an event loop in Node.js?

The event loop is a crucial concept in Node.js that enables it to handle asynchronous operations efficiently. It is essentially a mechanism that continuously checks the event queue and executes tasks when certain events occur.


Here’s how the event loop works:

  • Event Queue: Asynchronous tasks such as I/O operations, timers, and callbacks are placed in the event queue when they are initiated.
  • Event Loop: The event loop continuously checks the event queue for tasks to execute. It processes tasks one by one, in the order they were added to the queue.
  • Non-blocking I/O: While waiting for I/O operations to complete, the event loop doesn’t block the execution of other tasks. Instead, it moves on to the next task in the queue.
  • Callback Execution: When an asynchronous task completes, its corresponding callback function is pushed into the event queue. The event loop picks up these callbacks and executes them.


By efficiently managing asynchronous tasks and callbacks, the event loop ensures that Node.js remains responsive and can handle a large number of concurrent connections without consuming excessive resources.

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