Setting Up the Node.js Development Environment

Node.js is the foundation of every topic in this course. Before writing any API code, students need to understand what Node.js is, how it runs, and how to organize a project. This page explains the runtime, the package system, and the essential tools to build backend applications.

What Is Node.js?

Node.js is a JavaScript runtime environment built on Chrome’s V8 engine. It allows JavaScript code to run on a server (outside the browser). Before Node.js, JavaScript could only run in browsers.

Key characteristics

Feature	Explanation
Event-driven	Node.js uses events to trigger callbacks instead of waiting for operations to finish
Non-blocking I/O	While waiting for a file read or database query, Node continues processing other requests
Single-threaded	One thread handles all requests using the event loop (no multi-threading needed for most web apps)
V8 engine	The same JavaScript engine that powers Google Chrome, offering fast execution

Non-blocking I/O is what makes Node.js excellent for APIs and web servers. It handles many concurrent requests efficiently without spawning extra threads.

The Event Loop (Simplified)

The event loop is Node.js’s mechanism for handling asynchronous operations:

Call Stack — executes synchronous code line by line
Node APIs — handles async operations (fs, http, timers)
Callback Queue — queues completed async callbacks
Event Loop — moves callbacks from the queue to the call stack when it is empty

console.log('1 - synchronous');

setTimeout(() => {
  console.log('3 - async callback');
}, 0);

console.log('2 - synchronous');

// Output:
// 1 - synchronous
// 2 - synchronous
// 3 - async callback

Even with a 0ms timeout, the callback runs last because it goes through the event loop. This is fundamental to understanding asynchronous Node.js behavior.

npm: Node Package Manager

npm is the default package manager for Node.js. It lets you install, manage, and share reusable code packages from the npm registry.

Essential npm commands

# Initialize a new project (creates package.json)
npm init -y

# Install a production dependency
npm install express

# Install a dev-only dependency
npm install --save-dev nodemon

# Install a specific version
npm install express@4.18.2

# Uninstall a package
npm uninstall express

# Install all dependencies from package.json
npm install

# List installed packages
npm list

# Check for outdated packages
npm outdated

Understanding package.json

package.json is the project manifest. Every Node.js project has one.

{
  "name": "my-api",
  "version": "1.0.0",
  "description": "A sample REST API",
  "main": "index.js",
  "scripts": {
    "start": "node index.js",
    "dev": "nodemon index.js",
    "test": "jest"
  },
  "dependencies": {
    "express": "^4.18.2",
    "mongoose": "^7.6.0"
  },
  "devDependencies": {
    "nodemon": "^3.0.0",
    "jest": "^29.0.0"
  }
}

Field	Purpose
`name`	Package name (lowercase, no spaces)
`version`	Current version using semver (MAJOR.MINOR.PATCH)
`main`	Entry point file
`scripts`	Custom commands you can run with `npm run <name>`
`dependencies`	Packages needed in production
`devDependencies`	Packages needed only during development

nodemon for Development

nodemon watches your files and restarts the server automatically when code changes. Essential for development.

npm install --save-dev nodemon

{
  "scripts": {
    "dev": "nodemon index.js"
  }
}

npm run dev
# Server restarts on every file save

require() vs import/export

Node.js supports two module systems. You must know both.

// Import
const express = require('express');
const { helper } = require('./utils');

// Export
module.exports = { myFunction };
module.exports = myFunction;

// Import
import express from 'express';
import { helper } from './utils.js';

// Export
export { myFunction };
export default myFunction;

To use ES Modules, add to package.json:

{
  "type": "module"
}

You cannot mix require() and import in the same file. Choose one module system per project.

Your First HTTP Server (Built-in http module)

Before using Express, understand how Node’s built-in http module works. This is what Express wraps.

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

const server = http.createServer((req, res) => {
  res.writeHead(200, { 'Content-Type': 'application/json' });
  res.end(JSON.stringify({ message: 'Hello from Node.js!' }));
});

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

Run it:

node server.js

Your First Express Server

Express makes building servers much easier:

npm install express

// index.js
const express = require('express');
const app = express();
const PORT = process.env.PORT || 3000;

app.use(express.json()); // Parse incoming JSON

app.get('/', (req, res) => {
  res.status(200).json({ message: 'Hello World!' });
});

app.listen(PORT, () => {
  console.log(`Server running on http://localhost:${PORT}`);
});

node index.js
# Test: curl http://localhost:3000

.gitignore: What to Exclude

Always create a .gitignore before your first commit:

# .gitignore
node_modules/
.env
.env.*
*.log
dist/

Never commit node_modules (huge and platform-specific) or .env (contains secrets). These are the two most critical entries in .gitignore.

Key Terms to Memorize

Term	Definition
Runtime	The environment that executes code. Node.js is the runtime for server-side JavaScript.
Event loop	The mechanism that enables non-blocking async operations in Node.js.
Callback	A function passed as an argument to another function, called when an async operation completes.
Package	A reusable module of JavaScript code published to the npm registry.
Dependency	A package your production app needs to run.
devDependency	A package needed only during development (testing, linting, hot reload).
Semver	Semantic versioning: MAJOR.MINOR.PATCH format for package versions.
V8	Google’s JavaScript engine used in Chrome and Node.js.

Common Mistakes and Exam Tips

Forgetting npm install after cloning

When you clone a repo, node_modules is not included. Always run npm install first.

Using require and import in the same file

This causes a syntax error. CommonJS uses require/module.exports. ES Modules uses import/export. Pick one per project.

Not using nodemon in development

Restarting the server manually after every code change is slow. Add nodemon as a dev dependency and use npm run dev.

Wrong PORT causing EADDRINUSE errors

If port 3000 is already in use, change the port or kill the existing process. Use process.env.PORT || 3000 to read from environment variables.

Exam tip: Know the difference between dependencies and devDependencies in package.json. A common question asks which category a package like Jest (testing) or nodemon (dev server) belongs in. Both are devDependencies.

Node.js Setup

Database & APIs

What Is Node.js?

Key characteristics

The Event Loop (Simplified)

npm: Node Package Manager

Essential npm commands

Understanding package.json

nodemon for Development

require() vs import/export

Your First HTTP Server (Built-in http module)

Your First Express Server

.gitignore: What to Exclude

Key Terms to Memorize

Common Mistakes and Exam Tips

​What Is Node.js?

​Key characteristics

​The Event Loop (Simplified)

​npm: Node Package Manager

​Essential npm commands

​Understanding package.json

​nodemon for Development

​require() vs import/export

​Your First HTTP Server (Built-in http module)

​Your First Express Server

​.gitignore: What to Exclude

​Key Terms to Memorize

​Common Mistakes and Exam Tips

What Is Node.js?

Key characteristics

The Event Loop (Simplified)

npm: Node Package Manager

Essential npm commands

Understanding package.json

nodemon for Development

require() vs import/export

Your First HTTP Server (Built-in http module)

Your First Express Server

.gitignore: What to Exclude

Key Terms to Memorize

Common Mistakes and Exam Tips