Node.js Cheatsheet — Complete Developer Reference

Node.js is a powerful JavaScript runtime environment built on Chrome’s V8 engine that allows you to execute JavaScript on the server-side. It’s the backbone of modern web apps, APIs, and scalable microservices.

This Node.js Cheatsheet is designed as a quick and complete reference — ideal for developers learning backend programming or refreshing their knowledge.

What is Node.js?

Node.js enables developers to build fast, scalable, and real-time web applications using JavaScript beyond the browser.
It uses a non-blocking, event-driven I/O model, making it ideal for handling multiple requests efficiently.

✅ Key Features of Node.js:

• Built on V8 JavaScript Engine for speed
• Asynchronous and event-driven architecture
• Single-threaded but supports concurrent handling
• Huge ecosystem of packages via NPM
• Ideal for APIs, chat apps, and streaming servers

Installing Node.js

Check Node and NPM Versions

node -v
npm -v

Install a Package

npm install express

Initialize a Project

npm init -y

Node.js REPL Commands

Creating Your First Node.js Server

// server.js
const http = require('http');

const server = http.createServer((req, res) => {
  res.writeHead(200, {'Content-Type': 'text/plain'});
  res.end('Hello from Node.js Server!');
});

server.listen(3000, () => {
  console.log('Server running at http://localhost:3000');
});

Run:

node server.js

Node.js Core Modules

node.js cheatsheet, node.js tutorial, node.js examples, node.js file system, node.js server, express.js tutorial, node.js event loop, node.js asynchronous programming, node.js beginner guide, node.js quick reference

Working with File System (fs)

Read File

const fs = require('fs');
fs.readFile('example.txt', 'utf8', (err, data) => {
  if (err) throw err;
  console.log(data);
});

Write File

fs.writeFile('output.txt', 'Hello Node!', err => {
  if (err) throw err;
  console.log('File written successfully');
});

Append Data

fs.appendFile('log.txt', 'New log entry\n', err => {
  if (err) throw err;
});

Node.js Event Emitter

const EventEmitter = require('events');
const emitter = new EventEmitter();

emitter.on('message', (msg) => {
  console.log(`Received: ${msg}`);
});

emitter.emit('message', 'Hello Event System!');

Node.js Modules and Exports

module1.js

exports.greet = function(name) {
  return `Hello, ${name}!`;
};

main.js

const greet = require('./module1');
console.log(greet.greet('Developer'));

Node.js URL Module

const url = require('url');
const myURL = new URL('https://example.com/product?id=100&name=shirt');

console.log(myURL.hostname); // example.com
console.log(myURL.searchParams.get('name')); // shirt

Node.js OS Module

const os = require('os');
console.log(os.platform());
console.log(os.totalmem());
console.log(os.uptime());

Asynchronous Programming in Node.js

Node.js uses callbacks, promises, and async/await for asynchronous operations.

Using Promises

const fs = require('fs').promises;

async function readData() {
  const data = await fs.readFile('example.txt', 'utf8');
  console.log(data);
}
readData();

Node.js with Express Framework

Install Express:

npm install express

Example server:

const express = require('express');
const app = express();

app.get('/', (req, res) => {
  res.send('Welcome to Express Server');
});

app.listen(3000, () => {
  console.log('Server running on port 3000');
});

Node.js Middleware Example

app.use((req, res, next) => {
  console.log(`Request made at: ${new Date().toISOString()}`);
  next();
});

Node.js REST API Example

const express = require('express');
const app = express();
app.use(express.json());

let users = [{ id: 1, name: "John" }];

app.get('/users', (req, res) => res.json(users));
app.post('/users', (req, res) => {
  users.push(req.body);
  res.json({ message: "User added" });
});

app.listen(4000, () => console.log('API running on port 4000'));

Node.js Process Object

console.log(process.pid);
console.log(process.platform);
console.log(process.cwd());

Exit the process:

process.exit();

Node.js Best Practices

✅ Use environment variables with .env
✅ Handle errors using try...catch
✅ Use async/await instead of callbacks
✅ Organize routes and controllers properly
✅ Use a package manager (NPM/Yarn)

FAQ — Node.js Cheatsheet

Q1: What is Node.js used for?
Node.js is used to build fast, scalable, and real-time server-side applications using JavaScript.

Q2: Is Node.js a framework or runtime?
Node.js is a runtime environment, not a framework.

Q3: What makes Node.js asynchronous?
Its event-driven, non-blocking I/O system allows multiple requests to be processed simultaneously.

Q4: Can Node.js work with databases?
Yes, Node.js works with MySQL, MongoDB, PostgreSQL, and Redis seamlessly.

Q5: Is Node.js good for APIs?
Absolutely. Node.js is ideal for RESTful and GraphQL APIs due to its lightweight architecture.