memfs

This is a fork of https://www.npmjs.com/package/memfs, since there's a bunch of critical bugs and missing maintenance there, which might not be a priority for that project, but are definitely a priority for me (though I'm sending PR's). Upstream memfs has nearly 12 million downloads a week, so I can see why doing these changes would be really scary there!

Things I've done here include:

• update to newest jest, and increase maxWorkers for testing; fix an issue with one test
• update to newest typescript and node typings
• update target to es2020 from es5; this does make code run more efficiently and is much easier to debug if you want to directly edit node_modules
• fix the 13 security vulnerabilities revealed by npm audit
• upgrade prettier and switch to using the defaults
• switch to package-lock.json instead of yarn's lock
• fix chmodSync bug
• fix utimesSync bug
• fix realpathSync bug

See https://github.com/sagemathinc/memfs-js

---

Upstream description

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

• Node's fs API implemented, see old API Status, missing list, missing opendir
• Stores files in memory, in Buffers
• Throws sameish* errors as Node.js
• Has concept of i-nodes
• Implements hard links
• Implements soft links (aka symlinks, symbolic links)
• Permissions may* be implemented in the future
• Can be used in browser, see memfs-webpack

Install

1npm install --save memfs

Usage

1import { fs } from "memfs";
2
3fs.writeFileSync("/hello.txt", "World!");
4fs.readFileSync("/hello.txt", "utf8"); // World!

Create a file system from a plain JSON:

1import { fs, vol } from "memfs";
2
3const json = {
4  "./README.md": "1",
5  "./src/index.js": "2",
6  "./node_modules/debug/index.js": "3",
7};
8vol.fromJSON(json, "/app");
9
10fs.readFileSync("/app/README.md", "utf8"); // 1
11vol.readFileSync("/app/src/index.js", "utf8"); // 2

Export to JSON:

1vol.writeFileSync("/script.sh", "sudo rm -rf *");
2vol.toJSON(); // {"/script.sh": "sudo rm -rf *"}

Use it for testing:

1vol.writeFileSync("/foo", "bar");
2expect(vol.toJSON()).toEqual({ "/foo": "bar" });

Create as many filesystem volumes as you need:

1import { Volume } from "memfs";
2
3const vol = Volume.fromJSON({ "/foo": "bar" });
4vol.readFileSync("/foo"); // bar
5
6const vol2 = Volume.fromJSON({ "/foo": "bar 2" });
7vol2.readFileSync("/foo"); // bar 2

Use memfs together with unionfs to create one filesystem from your in-memory volumes and the real disk filesystem:

1import * as fs from "fs";
2import { ufs } from "unionfs";
3
4ufs.use(fs).use(vol);
5
6ufs.readFileSync("/foo"); // bar

Use fs-monkey to monkey-patch Node's require function:

1import { patchRequire } from "fs-monkey";
2
3vol.writeFileSync("/index.js", 'console.log("hi world")');
4patchRequire(vol);
5require("/index"); // hi world

Docs

• Reference
• Relative paths
• API status
• Dependencies

See also

• spyfs - spies on filesystem actions
• unionfs - creates a union of multiple filesystem volumes
• linkfs - redirects filesystem paths
• fs-monkey - monkey-patches Node's fs module and require function
• libfs - real filesystem (that executes UNIX system calls) implemented in JavaScript

License

Unlicense - public domain.