os-slash

Cross-platform, dependency-free JavaScript utility for consistent path normalization and manipulation.

Overview

os-slash is a lightweight utility library designed to handle file path transformations across multiple operating systems such as Windows, Linux, and macOS. It provides functions to:

• Convert Windows backslashes (\) to POSIX-style forward slashes (/) and vice versa
• Normalize paths by removing redundant slashes and trailing slashes
• Detect absolute paths on different platforms
• Safely join multiple path segments
• Calculate relative paths between two paths
• Manage trailing slashes (add or remove)
• Preserve special Windows extended-length paths (\\?\) intact

The library is written in pure JavaScript, has zero dependencies, and is compatible with Node.js, browsers, React, Angular, and any JavaScript environment.

Installation

npm install os-slash

Usage

Import individual functions as needed in your project:

import {
	slash,
	backslash,
	normalize,
	ensureTrailingSlash,
	removeTrailingSlash,
	isAbsolute,
	join,
	relative,
} from "os-slash";

API Reference

slash(path: string): string

Converts Windows-style backslashes (\) to forward slashes (/). Leaves Windows extended-length paths (starting with \\?\) unchanged.

Example:

console.log(slash("C:\\Users\\Alice\\Documents"));
// Output: C:/Users/Alice/Documents

console.log(slash("\\\\?\\C:\\Very\\Long\\Path"));
// Output: \\?\C:\Very\Long\Path  (unchanged)

backslash(path: string): string

Converts forward slashes (/) to Windows backslashes ().

backslash(path: string): string

Example:

console.log(backslash("C:/Users/Alice/Documents"));
// Output: C:\Users\Alice\Documents

normalize(path: string): string

Normalizes paths by converting backslashes to forward slashes, removing redundant slashes, and trimming trailing slashes except root /. Preserves extended-length Windows paths.

Example:

console.log(normalize("C:\\Users\\\\Alice\\/Documents\\/"));
// Output: C:/Users/Alice/Documents

console.log(normalize("////usr//local///bin/"));
// Output: /usr/local/bin

ensureTrailingSlash(path: string): string

Adds a trailing slash (/) if it is missing.

Example:

console.log(ensureTrailingSlash("C:/Users/Alice"));
// Output: C:/Users/Alice/

console.log(ensureTrailingSlash("/usr/local/bin/"));
// Output: /usr/local/bin/

removeTrailingSlash(path: string): string

Removes trailing slash (/) unless the path is root (/).

Example:

console.log(removeTrailingSlash("C:/Users/Alice/"));
// Output: C:/Users/Alice

console.log(removeTrailingSlash("/"));
// Output: /

isAbsolute(path: string): boolean

Detects if a path is absolute on Windows or POSIX.

POSIX: paths starting with / Windows: paths starting with drive letter + :\ or UNC paths starting with \

Example:

console.log(isAbsolute("/usr/local/bin")); // true
console.log(isAbsolute("C:\\Windows")); // true
console.log(isAbsolute("Documents/file")); // false

join(...paths: string[]): string

Joins multiple path segments into a single normalized path using forward slashes.

Example:

console.log(join("C:/Users", "Alice", "Documents"));
// Output: C:/Users/Alice/Documents
console.log(join("/usr", "local//", "/bin/"));
// Output: /usr/local/bin

relative(from: string, to: string): string

Calculates relative path from from to to.

Example:

console.log(relative("/Users/Alice/Documents", "/Users/Alice/Music"));
// Output: ../Music
console.log(relative("C:/Projects/app/src", "C:/Projects/app/tests"));
// Output: ../tests