Path

JavaScript · Reference cheat sheet

📋 Overview

Node.js node:path builds and inspects filesystem paths. Prefer path.join / path.resolve over string concatenation so separators and .. segments stay correct across platforms.

import path from "node:path";

🔧 Core concepts

• join(...parts): concatenates segments; normalizes . / ..; does not resolve against cwd.
• resolve(...parts): produces an absolute path from right to left; uses process.cwd() when needed.
• dirname / basename / extname: parent dir, final segment, and extension (including the dot).
• parse / format: object with root, dir, base, name, ext.
• sep: \ on Windows, / on POSIX.
• path.posix / path.win32: force POSIX or Windows rules regardless of host OS (useful for URLs or cross-platform config).

💡 Examples

import path from "node:path";
import { fileURLToPath } from "node:url";

path.join("logs", "app", "out.txt");
// 'logs/app/out.txt' (POSIX) or 'logs\\app\\out.txt' (win32)

path.resolve("data", "../config.json");
// absolute path ending in config.json

path.dirname("/var/app/index.js"); // '/var/app'
path.basename("/var/app/index.js"); // 'index.js'
path.basename("/var/app/index.js", ".js"); // 'index'
path.extname("photo.tar.gz"); // '.gz'

const p = path.parse("/home/ada/report.pdf");
// { root: '/', dir: '/home/ada', base: 'report.pdf',
//   ext: '.pdf', name: 'report' }

path.format({ dir: "/tmp", base: "a.txt" }); // '/tmp/a.txt'

// ESM __dirname equivalent
const __filename = fileURLToPath(import.meta.url);
const __dirname = path.dirname(__filename);

// Always forward slashes (e.g. virtual paths)
path.posix.join("a", "b", "c"); // 'a/b/c'

⚠️ Pitfalls

• join does not make a path absolute; use resolve when you need that.
• extname returns only the last extension (.gz for a.tar.gz).
• Mixing path.win32 and path.posix incorrectly breaks joins; pick one style for a given string format.
• Trailing separators are normalized away by join / resolve (except root).
• Do not use path for URL paths — use URL / url helpers instead.

🔗 Related

• Node URL helpers — pathToFileURL / fileURLToPath
• URL — WHATWG URL in JS
• CommonJS modules — __dirname / __filename
• ESM import/export — import.meta.url
• fs — reading/writing with resolved paths