Node.js – Synchronous vs Asynchronous | Node.js Tutorial

📌 What are Sync vs Async?

What is Synchronous and Asynchronous in Node.js?

This tutorial explains the difference between synchronous (blocking) and asynchronous (non-blocking) architectures, and how Node.js handles them.

🟢 Synchronous

Synchronous is a blocking architecture, so the execution of each operation depends on completing the one before it.
Each task requires an answer before moving on to the next iteration.

🔵 Asynchronous

Asynchronous is a non-blocking architecture, so the execution of one task isn't dependent on another.
Tasks can run simultaneously (parallel).

⚖️ Synchronous VS Asynchronous

Async is multi-threaded; operations can run in parallel.
Sync is single-threaded; only one operation runs at a time.
Async is non-blocking; it can send multiple requests to a server.
Sync is blocking; it sends one request at a time and waits for a response.
Async increases throughput because multiple operations can run simultaneously.
Sync is slower and more methodical.

❓ Is Node.js Sync or Async?

Node.js primarily follows an Asynchronous model, but synchronous methods are also available when needed.

Node.js Environment

RUNTIME ACTIVE

const fs = require('fs');

console.log("--- START ---");

// Asynchronous read (non-blocking)
fs.readFile('./package.json', 'utf8', (err, data) => {
  console.log("Async Read Finished");
});

console.log("--- END (Main thread) ---");

Terminal Output

Live Output Preview

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