memfs
Advanced tools
Package description
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.
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.txtFile 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();mock-fs is a package that provides a mock file system for Node.js. It is similar to memfs in that it allows you to create an in-memory file system for testing purposes. However, mock-fs overrides the native fs module, while memfs provides a separate file system instance.
unionfs is a package that can combine multiple file systems into a single cohesive file system interface. It can be used with memfs to overlay an in-memory file system on top of the real file system, providing a way to mix real and virtual file system operations.
fs-mock is another in-memory file system module for Node.js. It offers similar functionality to memfs, allowing you to mock the fs module for testing. It differs in API and implementation details, and the choice between fs-mock and memfs may come down to personal preference or specific use-case requirements.
Changelog
4.1.0-next.1 (2023-06-21)
Readme
JavaScript file system utilities for Node.js and browser.
npm i memfs
fs APIexperimental fs to File System Access API adapterexperimental File System Access API to fs adapterexperimental crudfs a CRUD-like file system abstractionfs in browser, creates a .tar file in real folderfs in browser, synchronous API, writes to real folderspyfs - spies on filesystem actionsunionfs - creates a union of multiple filesystem volumeslinkfs - redirects filesystem pathsfs-monkey - monkey-patches Node's fs module and require functionApache 2.0
FAQs
In-memory file-system with Node's fs API.
We found that memfs demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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