🌀 nodejs-event-loop-simulator

A minimal and educational simulation of Node.js event loop phases — including process.nextTick, microtasks (Promise.then), timers, poll, check, and close callbacks.

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📚 Overview

This project is designed to help developers understand the internal workings of the Node.js Event Loop by simulating each phase step-by-step.

It supports queuing callbacks for:

• nextTick (like process.nextTick)
• Microtasks (like Promise.then)
• Timers (like setTimeout)
• Pending callbacks (e.g., I/O like fs.readFile)
• Idle/Prepare (internal phases)
• Poll (I/O polling)
• Check (like setImmediate)
• Close callbacks (e.g., socket .on('close'))

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🚀 Getting Started

1. Clone the repository

git clone https://github.com/your-username/event-loop-simulator.git
cd event-loop-simulator

2. Run the simulation

node index.js

✨ Example Usage

const EventLoopSimulator = require('./event-loop');

const eventLoop = new EventLoopSimulator();

eventLoop.queueNextTick(() => console.log('nextTick callback'));
eventLoop.queueMicrotask(() => console.log('microtask callback'));
eventLoop.queueTimer(() => console.log('timer callback'));

eventLoop.tick();

🔄 Supported Phases and Methods

Phase ------------------------ Method
Next Tick -------------------- queueNextTick(cb)
Microtask -------------------- queueMicrotask(cb)
Timer ------------------------ queueTimer(cb)
Pending Callback ------------- queuePendingCallback(cb)
Idle/Prepare ----------------- queueIdlePrepare(cb)
Poll ------------------------- queuePoll(cb)
Check ------------------------ queueCheck(cb)
Close ------------------------ queueCloseCallback(cb)

🎯 Purpose

This simulator is intended for educational purposes only. It helps visualize the order and behavior of various phases in the Node.js event loop without using real asynchronous APIs.

📄 License

MIT License