Node.js path module: handling file paths correctly cross-platform

Always Use path — Never Concatenate Strings

Manual string concatenation for file paths breaks on Windows which uses backslashes. The path module handles separators correctly on every platform.

const path = require('path');

path.join('/home', 'user', 'docs', 'file.txt');
// POSIX: /home/user/docs/file.txt

path.resolve('src', 'index.js');
// absolute path from cwd

path.dirname('/home/user/file.txt');  // /home/user
path.basename('/home/user/file.txt'); // file.txt
path.extname('/home/user/file.txt');  // .txt

path.join vs path.resolve

// path.join: concatenates with correct separator
path.join('a', 'b', 'c'); // a/b/c

// path.resolve: builds absolute path from right to left
path.resolve('a', '/b', 'c'); // /b/c (stops at absolute)
path.resolve('a', 'b');       // /cwd/a/b (prepends cwd)

Parsing and Building Paths

const info = path.parse('/home/user/notes.txt');
// { root: '/', dir: '/home/user', base: 'notes.txt',
//   ext: '.txt', name: 'notes' }

const rebuilt = path.format(info); // /home/user/notes.txt