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memfs

In-memory file-system with Node's fs API.

    4.7.7latest
    GitHub
    npm

Version published
Maintainers
1
Weekly downloads
14,915,691
increased by4.23%

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Package description

What is memfs?

The memfs npm package is an in-memory filesystem that mimics the Node.js fs module. It allows you to create an ephemeral file system that resides entirely in memory, without touching the actual disk. This can be useful for testing, mocking, and various other scenarios where you don't want to perform I/O operations on the real file system.

What are memfs's main functionalities?

Creating and manipulating files

This feature allows you to create, read, and write files in memory as if you were using the native fs module.

const { Volume } = require('memfs');
const vol = new Volume();
vol.writeFileSync('/hello.txt', 'Hello, World!');
const content = vol.readFileSync('/hello.txt', 'utf8');
console.log(content); // Outputs: Hello, World!

Directory operations

This feature enables you to create directories, list their contents, and perform other directory-related operations, all in memory.

const { Volume } = require('memfs');
const vol = new Volume();
vol.mkdirSync('/mydir');
vol.writeFileSync('/mydir/file.txt', 'My file content');
const files = vol.readdirSync('/mydir');
console.log(files); // Outputs: ['file.txt']

Linking and symlinking

This feature allows you to create hard links and symbolic links, mimicking the behavior of links on a real file system.

const { Volume } = require('memfs');
const vol = new Volume();
vol.writeFileSync('/original.txt', 'Content of original');
vol.linkSync('/original.txt', '/link.txt');
vol.symlinkSync('/original.txt', '/symlink.txt');
const linkContent = vol.readFileSync('/link.txt', 'utf8');
const symlinkContent = vol.readlinkSync('/symlink.txt');
console.log(linkContent); // Outputs: Content of original
console.log(symlinkContent); // Outputs: /original.txt

File system watching

This feature provides the ability to watch for changes in the file system, similar to fs.watch in the native fs module.

const { Volume } = require('memfs');
const vol = new Volume();
const fs = vol.promises;

async function watchExample() {
  await fs.writeFile('/watched.txt', 'Initial content');
  fs.watch('/watched.txt', (eventType, filename) => {
    console.log(`Event type: ${eventType}; File: ${filename}`);
  });
  await fs.writeFile('/watched.txt', 'Updated content');
}

watchExample();

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Changelog

Source

4.7.7 (2024-02-21)

Bug Fixes

  • accept file names beginning with a period (#1005) (3c18dae)

Readme

Source

memfs

JavaScript file system utilities for Node.js and browser.

Install

npm i memfs

Docs

Demos

See also

  • unionfs - creates a union of multiple filesystem volumes
  • fs-monkey - monkey-patches Node's fs module and require function
  • linkfs - redirects filesystem paths
  • spyfs - spies on filesystem actions

License

Apache 2.0

Keywords

FAQs

Last updated on 21 Feb 2024

Did you know?

Socket installs a GitHub app to automatically flag issues on every pull request and report the health of your dependencies. Find out what is inside your node modules and prevent malicious activity before you update the dependencies.

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