memfs

In-memory file system with Node.js fs API and browser File System (Access) API.

Overview

memfs is a JavaScript library that implements an in-memory file system compatible with Node.js fs module and the browser File System (Access) API. Use it for testing, mocking file systems, or creating virtual file systems in both Node.js and browser environments.

Installation

npm install memfs

Quick Start

Node.js fs API

import { fs } from 'memfs';

// Write a file
fs.writeFileSync('/hello.txt', 'Hello, World!');

// Read a file
const content = fs.readFileSync('/hello.txt', 'utf-8');
console.log(content); // "Hello, World!"

// Create a directory
fs.mkdirSync('/mydir');

// List directory contents
console.log(fs.readdirSync('/')); // ['hello.txt', 'mydir']

Browser File System API

import { fsa } from 'memfs';

// Get root directory handle
const root = await fsa.getRoot();

// Create a file
const file = await root.getFileHandle('hello.txt', { create: true });
const writable = await file.createWritable();
await writable.write('Hello, World!');
await writable.close();

// Read the file
const readable = await file.getFile();
const text = await readable.text();
console.log(text); // "Hello, World!"

Features

• Node.js fs module API compatibility
• Browser File System (Access) API implementation
• Adapters between fs and File System API
• Directory snapshots and tree printing utilities
• Works in Node.js and modern browsers
• TypeScript support

Documentation

For detailed documentation and more examples, visit the main project page.

License

Apache 2.0