Node.js Fundamentals

Chapter 8: Working with Paths and URLs

8.1 Path Module

The path module provides utilities for working with file and directory paths. It handles cross-platform path differences.

Path Joining:

const path = require('path');

// Join path segments (handles slashes automatically)
const filePath = path.join(__dirname, 'public', 'index.html');
// Windows: C:projectpublicindex.html
// Unix: /project/public/index.html

// Resolve to absolute path
const absolutePath = path.resolve('public', 'index.html');
// Resolves from current working directory

Path Parsing:

const path = require('path');

const filePath = '/users/john/documents/file.txt';

// Get different parts of path
path.dirname(filePath);   // /users/john/documents
path.basename(filePath);  // file.txt
path.extname(filePath);   // .txt
path.parse(filePath);
// {
//   root: '/',
//   dir: '/users/john/documents',
//   base: 'file.txt',
//   ext: '.txt',
//   name: 'file'
// }

Path Utilities:

// Normalize path (remove redundant separators)
path.normalize('/foo/bar//baz/'); // /foo/bar/baz/

// Check if absolute path
path.isAbsolute('/foo/bar'); // true
path.isAbsolute('./foo');     // false

// Get relative path
path.relative('/users/john', '/users/jane'); // ../jane

8.2 URL Module

The url module provides utilities for URL resolution and parsing.

Parsing URLs:

const url = require('url');

const urlString = 'https://example.com:8080/path?query=value#hash';

const parsed = url.parse(urlString, true);
// {
//   protocol: 'https:',
//   host: 'example.com:8080',
//   hostname: 'example.com',
//   port: '8080',
//   pathname: '/path',
//   query: { query: 'value' },
//   hash: '#hash'
// }

// Access query parameters
const queryValue = parsed.query.query; // 'value'

URL Object (Modern API):

// Using URL constructor (ES6)
const myUrl = new URL('https://example.com/path?query=value');

console.log(myUrl.hostname); // example.com
console.log(myUrl.pathname); // /path
console.log(myUrl.searchParams.get('query')); // value

// Modify URL
myUrl.searchParams.set('newParam', 'newValue');
console.log(myUrl.toString());
// https://example.com/path?query=value&newParam=newValue

URL Building:

const url = require('url');

// Build URL from parts
const urlObject = {
    protocol: 'https',
    host: 'example.com',
    pathname: '/api/users',
    query: { id: 123 }
};

const urlString = url.format(urlObject);
// https://example.com/api/users?id=123

8.3 Working with File Paths

Common operations when working with file paths.

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

// Get current file's directory
const currentDir = __dirname;

// Build path to file
const configPath = path.join(__dirname, 'config', 'settings.json');

// Check if file exists
if (fs.existsSync(configPath)) {
    const config = require(configPath);
}

// Get file extension
const ext = path.extname('image.jpg'); // .jpg

// Change extension
const newPath = path.join(
    path.dirname('file.txt'),
    path.basename('file.txt', '.txt') + '.js'
); // file.js

8.4 Cross-Platform Considerations

Path module handles platform differences automatically.

• Use path.join() instead of string concatenation
• Don't hardcode path separators (/ or )
• Use path.resolve() for absolute paths
• Test on different platforms when possible