---
title: Node.js Basics 
description: A guide to the basics of Node.js
tags:
  - node.js
  - javascript
  - programming
  - web development
---

# Node.js Basics Guide

## What is Node.js?

Node.js is an open-source, cross-platform JavaScript runtime environment that executes JavaScript code outside a web browser. It allows developers to use JavaScript to write command-line tools and server-side scripts.

## Key Features

- **Non-blocking I/O**: Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient.
- **NPM (Node Package Manager)**: Provides access to a large ecosystem of open-source packages.
- **Single-threaded but highly scalable**: Uses an event loop to handle multiple connections concurrently.

## Installation

### Install Node.js

Download and install from [nodejs.org](https://nodejs.org/), or use package managers:

```bash
# macOS (using Homebrew)
brew install node

# Ubuntu/Debian
sudo apt update
sudo apt install nodejs npm

# Windows
# Download the installer from nodejs.org
```

Verify installation:

```bash
node -v
npm -v
```

## Creating Your First Node.js Application

1. Create a directory for your project:

```bash
mkdir my-first-node-app
cd my-first-node-app
```

2. Initialize a new Node.js project:

```bash
npm init -y
```

3. Create a file named `app.js`:

```javascript
console.log("Hello, Node.js!");
```

4. Run your application:

```bash
node app.js
```

## Built-in Modules

Node.js comes with several built-in modules that you can use without installation:

### File System (fs)

```javascript
const fs = require("fs");

// Read a file
fs.readFile("example.txt", "utf8", (err, data) => {
  if (err) throw err;
  console.log(data);
});

// Write to a file
fs.writeFile("example.txt", "Hello, Node.js!", (err) => {
  if (err) throw err;
  console.log("File has been saved!");
});
```

### HTTP

```javascript
const http = require("http");

const server = http.createServer((req, res) => {
  res.statusCode = 200;
  res.setHeader("Content-Type", "text/plain");
  res.end("Hello World\n");
});

server.listen(3000, "127.0.0.1", () => {
  console.log("Server running at http://127.0.0.1:3000/");
});
```

### Path

```javascript
const path = require("path");

// Join path segments
console.log(path.join("/home", "user", "documents", "file.txt"));
// Output: /home/user/documents/file.txt

// Get the file extension
console.log(path.extname("file.txt"));
// Output: .txt
```

## NPM Packages

NPM (Node Package Manager) allows you to install and manage third-party packages.

### Installing Packages

```bash
# Install a package and save it as a dependency
npm install express

# Install a package and save it as a dev dependency
npm install nodemon --save-dev
```

### Using Packages

```javascript
const express = require("express");
const app = express();

app.get("/", (req, res) => {
  res.send("Hello from Express!");
});

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

## Asynchronous Programming

Node.js is built around asynchronous programming. There are several ways to handle asynchronous operations:

### Callbacks

```javascript
fs.readFile("file.txt", "utf8", (err, data) => {
  if (err) {
    console.error("Error reading file:", err);
    return;
  }
  console.log(data);
});
```

### Promises

```javascript
const fs = require("fs").promises;

fs.readFile("file.txt", "utf8")
  .then((data) => {
    console.log(data);
  })
  .catch((err) => {
    console.error("Error reading file:", err);
  });
```

### Async/Await

```javascript
const fs = require("fs").promises;

async function readFile() {
  try {
    const data = await fs.readFile("file.txt", "utf8");
    console.log(data);
  } catch (err) {
    console.error("Error reading file:", err);
  }
}

readFile();
```

## Event Emitters

Node.js uses an event-driven architecture with many objects that emit events:

```javascript
const EventEmitter = require("events");

class MyEmitter extends EventEmitter {}

const myEmitter = new MyEmitter();

// Register an event listener
myEmitter.on("event", () => {
  console.log("An event occurred!");
});

// Emit the event
myEmitter.emit("event");
```

## Error Handling

### Try-Catch Blocks

```javascript
try {
  // Code that might throw an error
  const data = JSON.parse(invalidJson);
} catch (err) {
  console.error("Error parsing JSON:", err);
}
```

### Handling Uncaught Exceptions

```javascript
process.on("uncaughtException", (err) => {
  console.error("Uncaught exception:", err);
  // Perform cleanup operations
  process.exit(1);
});
```

## Resources for Further Learning

- [Official Node.js Documentation](https://nodejs.org/en/docs/)
- [Node.js API Reference](https://nodejs.org/api/)
- [NPM Documentation](https://docs.npmjs.com/)
- [Express.js Documentation](https://expressjs.com/)

## Debugging Node.js Applications

- Using the `--inspect` flag: `node --inspect app.js`
- Using Visual Studio Code's built-in debugger
- Using the `debug` npm package

## Next Steps

- Learn Express.js for building web applications
- Explore databases like MongoDB or PostgreSQL with Node.js
- Study authentication and security in Node.js applications
- Learn about RESTful API design principles