W260426/14.webpack/node_modules/memfs/docs/text.md

memfs is an in-memory file system. It implements two APIs:

• Node's fs module --- a drop-in replacement you can use anywhere the fs module is expected (tests, mocks, bundlers, sandboxes). Files live in memory instead of on disk.
• The browser File System Access (FSA) API --- the same FileSystemDirectoryHandle interface a browser exposes, backed by memory.

It also ships adapters that translate between those two APIs, so you can run fs-based code in the browser on top of a real directory, or expose an fs-like filesystem through FSA handles. It runs in Node.js, Deno, Bun, and browsers, and stores file contents in Uint8Array buffers.

import { fs } from 'memfs';

fs.writeFileSync('/hello.txt', 'Hello, World!');
fs.readFileSync('/hello.txt', 'utf8'); // 'Hello, World!'

fs.mkdirSync('/dir');
fs.readdirSync('/'); // ['dir', 'hello.txt']

Install

npm install memfs

Two ways in

The default export gives you a ready-to-use filesystem. fs is a bound, require('fs')-shaped object --- vol is the Volume behind it. They share the same storage.

import { fs, vol } from 'memfs';

fs.writeFileSync('/script.sh', 'sudo rm -rf *');
vol.toJSON(); // {'/script.sh': 'sudo rm -rf *'}

For an isolated filesystem (recommended for tests, so volumes never bleed into each other), call memfs() --- it returns a fresh fs/vol pair, optionally seeded from a JSON tree:

import { memfs } from 'memfs';

const { fs, vol } = memfs({ '/app/index.js': 'console.log(1)' });

fs.readFileSync('/app/index.js', 'utf8'); // 'console.log(1)'

Surface map

Page	Import	What it covers
Node fs API	memfs	The fs/vol/Volume/memfs() model and the full Node fs method surface
Volumes	memfs	Building volumes from JSON, exporting them, and unionfs / fs-monkey integration
File System Access	memfs/lib/fsa	An in-memory FSA filesystem (FileSystemDirectoryHandle and friends)
Adapters	memfs/lib/node-to-fsa, memfs/lib/fsa-to-node	Convert between the fs API and the FSA API in either direction
Snapshots	@jsonjoy.com/fs-snapshot	POJO / CBOR / JSON snapshots of any fs directory
Tree printing	@jsonjoy.com/fs-print	Print an ASCII tree of any fs directory

`memfs` is built from a set of smaller `@jsonjoy.com/fs-*` packages
(`fs-node`, `fs-fsa`, `fs-node-to-fsa`, `fs-fsa-to-node`, `fs-snapshot`,
`fs-print`, ...). Installing `memfs` pulls them all in; the snapshot and
tree-printing utilities are also publishable on their own.