Using Built-in Modules like FS and HTTP

1. Introduction

This tutorial aims to familiarize you with two of Node.js's built-in modules: fs and http. These modules are used for handling files and establishing servers, respectively.

By the end of this tutorial, you'll be able to read, write, and delete files using the fs module. You'll also learn how to create a basic HTTP server using the http module.

Prerequisites: Basic knowledge of JavaScript and Node.js is recommended.

2. Step-by-Step Guide

The Node.js filesystem (fs) module allows you to interact with the file system on your computer. It can be used to perform CRUD (Create, Read, Update, Delete) operations on files and directories.

The HTTP (http) module stands for HyperText Transfer Protocol. It's a protocol used to transfer data over the web. In Node.js, the http module allows you to transfer data over the internet.

Let's explore these modules further.

The FS Module

The fs module can be included in your application as follows:

const fs = require('fs');

Reading Files

To read a file, use the fs.readFile() method:

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

In this example, test.txt is the name of the file we want to read. utf8 is the character encoding, and the function (err, data) is a callback function that returns the file content (data).

Writing Files

The fs.writeFile() method is used for writing new files:

fs.writeFile('test.txt', 'Hello, World!', (err) => {
  if (err) throw err;
  console.log('File has been saved!');
});

Here, Hello, World! is the text we want to write to test.txt.

The HTTP Module

Include the http module in your application as follows:

const http = require('http');

Creating a Server

To create a server, use the http.createServer() method:

const server = http.createServer((req, res) => {
  res.end('Hello, World!');
});

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

In this example, the server listens on port 3000. When a client connects, the server responds with "Hello, World!".

3. Code Examples

Example 1: Reading a File

const fs = require('fs');

fs.readFile('test.txt', 'utf8', (err, data) => {
  if (err) {
    console.log(err);
  } else {
    console.log(data);
  }
});

In this example, the readFile method is used to read a file named test.txt. The utf8 parameter specifies the encoding. The function (err, data) is a callback that is invoked after the file has been read. It logs the file's content to the console.

Example 2: Creating a Server

const http = require('http');

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

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

In this example, the http module's createServer method is used to create an HTTP server. The server listens on port 3000 and responds with "Hello, World!" to any requests.

4. Summary

In this tutorial, we've covered how to use the fs and http modules in Node.js. You've learned how to read and write files with fs, and how to create a server with http.

To continue your learning, explore other built-in Node.js modules and practice using them in your projects. For more information, visit the Node.js Docs.

5. Practice Exercises

Exercise 1: Write a JavaScript program that uses the fs module to create a new file named myFile.txt and write "This is my file" in it.

Exercise 2: Write a JavaScript program that uses the http module to create a server. The server should respond with "Welcome to my server!" when accessed.

Exercise 3: Write a JavaScript program that uses both the fs and http modules. When the server is accessed, it should read a file named myFile.txt and display its content.

Solution 1:

const fs = require('fs');

fs.writeFile('myFile.txt', 'This is my file', (err) => {
  if (err) throw err;
  console.log('File has been saved!');
});

Solution 2:

const http = require('http');

const server = http.createServer((req, res) => {
  res.end('Welcome to my server!');
});

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

Solution 3:

const fs = require('fs');
const http = require('http');

const server = http.createServer((req, res) => {
  fs.readFile('myFile.txt', 'utf8', (err, data) => {
    if (err) throw err;
    res.end(data);
  });
});

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