BrowserFS

BrowserFS is an in-browser file system that emulates the Node JS file system API and supports storing and retrieving files from various backends. BrowserFS also integrates nicely into the Emscripten file system.

Releases and compatibility going forward

I am currently working on getting NPM permissions from John Vilk (jvilk), the creator of BrowserFS. He is very busy with life and does not have the time to work on BrowserFS. That includes adminministration actions like giving me the aforementioned permissions. Until I get permissions to publish BrowserFS, no new releases of the browserfs package can be published on NPM. You will need to build from source for now.

In addition, I am working on obtaining the browserfs organization names on GitHub and NPM. Once that is done, the repository will be moved to BrowserFS/BrowserFS and some package reorgnization will be done. The new structure will look like this:

| NPM package | Description | | ----------- | -------- | | @browserfs/core | Includes the core code for BrowserFS and these backends: InMemory, MountableFileSystem, OverlayFS, AsyncMirror, FolderAdapter | | @browserfs/fetch | Fetch/HTTPRequest/XMLHTTPRequest backend | | @browserfs/dom | Backends which require DOM APIs (i.e. LocalStorage and IndexedDB) | | @browserfs/emscripten | Emscripten backend | | @browserfs/zip | ZipFS backend (will be updated to include explode, unreduce, and unshrink) | | @browserfs/iso | IsoFS backend | | @browserfs/dropbox | Dropbox backend |

This will be done so users of browserfs don't bundle 5x more code than they actually need and so the library's bundles are smaller.

- Vortex (current BrowserFS maintainer)

Backends

BrowserFS is highly extensible, and ships with many filesystem backends:

• HTTPRequest: Downloads files on-demand from a webserver using fetch.
• LocalStorage: Stores files in the browser's localStorage.
• IndexedDB: Stores files into the browser's IndexedDB object database.
• Dropbox: Stores files into the user's Dropbox account.
  • Note: You provide this filesystem with an authenticated DropboxJS V2 JS SDK client.
• InMemory: Stores files in-memory. Thus, it is a temporary file store that clears when the user navigates away.
• ZipFS: Read-only zip file-backed FS. Lazily decompresses files as you access them.
  • Supports DEFLATE out-of-the-box.
  • Have super old zip files? The browserfs-zipfs-extras package adds support for EXPLODE, UNREDUCE, and UNSHRINK.
• IsoFS: Mount an .iso file into the file system.
  • Supports Microsoft Joliet and Rock Ridge extensions to the ISO9660 standard.
• WorkerFS: Lets you mount the BrowserFS file system configured in the main thread in a WebWorker, or the other way around!
• MountableFileSystem: Lets you mount multiple file systems into a single directory hierarchy, as in -nix-based OSes.
• OverlayFS: Mount a read-only file system as read-write by overlaying a writable file system on top of it. Like Docker's overlayfs, it will only write changed files to the writable file system.
• AsyncMirror: Use an asynchronous backend synchronously. Invaluable for Emscripten; let your Emscripten applications write to larger file stores with no additional effort!
  • Note: Loads the entire contents of the file system into a synchronous backend during construction. Performs synchronous operations in-memory, and enqueues them to be mirrored onto the asynchronous backend.
• FolderAdapter: Wraps a file system, and scopes all interactions to a subfolder of that file system.
• Emscripten: Lets you mount Emscripten file systems inside BrowserFS.

More backends can be defined by separate libraries, so long as they extend they implement BrowserFS.FileSystem. Multiple backends can be active at once at different locations in the directory hierarchy.

For more information, see the API documentation for BrowserFS.

Building

Prerequisites:

• Node and NPM
• Run npm install (or the equivilent command using your package manager) to install local dependencies.

After running npm run build, you can find built versions in the dist directory.

Custom builds (not recommended):

If you want to build BrowserFS with a subset of the available backends, change src/core/backends.ts to include only the backends you require, and re-build.

Usage

🛈 The examples are written in ESM. If you aren't using ESM, you can add <script src="browserfs.min.js"></script> to your HTML and use BrowserFS via the global BrowserFS object.

BrowserFS provides a convient configure function which you can use to easily configure BrowserFS to use a variety of file system types.

Here's a simple usage example using the LocalStorage-backed file system:

import { configure, BFSRequire } from 'browserfs';

// you can also add a callback as the last parameter instead of using promises
await configure({ fs: 'LocalStorage' });

const fs = BFSRequire('fs');

// Now, you can write code like this:

fs.writeFile('/test.txt', 'Cool, I can do this in the browser!', function(err) {
	fs.readFile('/test.txt', function(err, contents) {
		console.log(contents.toString());
	});
});

The following code mounts a zip file to /zip, in-memory storage to /tmp, and IndexedDB browser-local storage to /home:

import { configure, BFSRequire } from 'browserfs';
import Buffer from 'buffer';

const zipData = await (await fetch('mydata.zip')).arrayBuffer();

await configure({
	fs: 'MountableFileSystem',
	options: {
		'/mnt/zip': {
			fs: 'ZipFS',
			options: {
				zipData: Buffer.from(zipData)
			}
		},
		'/tmp': { fs: 'InMemory' },
		'/home': { fs: 'IndexedDB' }
	}
};

Using with Browserify and Webpack

BrowserFS is published as a UMD module, so you can either include it on your webpage in a script tag or bundle it with your favorite JavaScript module bundler.

You can also use BrowserFS to supply your application with fs, path, and buffer modules, as well as the Buffer and process globals. BrowserFS contains shim modules for fs, buffer, path, and process that you can use with Webpack and Browserify.

Webpack:

module.exports = {
  resolve: {
    // Use our versions of Node modules.
		alias: {
      'fs': 'browserfs/dist/shims/fs.js',
      'buffer': 'browserfs/dist/shims/buffer.js',
      'path': 'browserfs/dist/shims/path.js',
      'processGlobal': 'browserfs/dist/shims/process.js',
      'bufferGlobal': 'browserfs/dist/shims/bufferGlobal.js',
      'bfsGlobal': require.resolve('browserfs')
    }
  },
  // REQUIRED to avoid issue "Uncaught TypeError: BrowserFS.BFSRequire is not a function"
  // See: https://github.com/jvilk/BrowserFS/issues/201
  module: {
    noParse: /browserfs\.js/
  },
  plugins: [
    // Expose BrowserFS, process, and Buffer globals.
    // NOTE: If you intend to use BrowserFS in a script tag, you do not need
    // to expose a BrowserFS global.
    new webpack.ProvidePlugin({ BrowserFS: 'bfsGlobal', process: 'processGlobal', Buffer: 'bufferGlobal' })
  ],
  // DISABLE Webpack's built-in process and Buffer polyfills!
  node: {
    process: false,
    Buffer: false
  }
};

Browserify:

var browserfsPath = require.resolve('browserfs');
var browserifyConfig = {
  // Override Browserify's builtins for buffer/fs/path.
  builtins: Object.assign({}, require('browserify/lib/builtins'), {
    "buffer": require.resolve('browserfs/dist/shims/buffer.js'),
    "fs": require.resolve("browserfs/dist/shims/fs.js"),
    "path": require.resolve("browserfs/dist/shims/path.js")
  }),
  insertGlobalVars: {
    // process, Buffer, and BrowserFS globals.
    // BrowserFS global is not required if you include browserfs.js
    // in a script tag.
    "process": function () { return "require('browserfs/dist/shims/process.js')" },
    'Buffer': function () { return "require('buffer').Buffer" },
    "BrowserFS": function() { return "require('" + browserfsPath + "')" }
  }
};

Using with Node

You can use BrowserFS with Node. Simply add browserfs as an NPM dependency, and require('browserfs'). The object returned from this action is the same BrowserFS global described above.

If you need BrowserFS to return Node Buffer objects (instead of objects that implement the same interface), simply require('browserfs/dist/node/index') instead.

Using with Emscripten

You can use any synchronous BrowserFS file systems with Emscripten! Persist particular folders in the Emscripten file system to localStorage, or enable Emscripten to synchronously download files from another folder as they are requested.

Include browserfs.min.js into the page, and configure BrowserFS prior to running your Emscripten code. Then, add code similar to the following to your Module's preRun array:

/**
 * Mounts a localStorage-backed file system into the /data folder of Emscripten's file system.
 */
function setupBFS() {
	// Grab the BrowserFS Emscripten FS plugin.
	var BFS = new BrowserFS.EmscriptenFS();
	// Create the folder that we'll turn into a mount point.
	FS.createFolder(FS.root, 'data', true, true);
	// Mount BFS's root folder into the '/data' folder.
	FS.mount(BFS, {root: '/'}, '/data');
}

Note: Do NOT use BrowserFS.install(window) on a page with an Emscripten application! Emscripten will be tricked into thinking that it is running in Node JS.

If you wish to use an asynchronous BrowserFS backend with Emscripten (e.g. Dropbox), you'll need to wrap it into an AsyncMirror file system first:

/**
 * Run this prior to starting your Emscripten module.
 * @param dropboxClient An authenticated DropboxJS client.
 */
function asyncSetup(dropboxClient, cb) {
	// This wraps Dropbox in the AsyncMirror file system.
	// BrowserFS will download all of Dropbox into an
	// InMemory file system, and mirror operations to
	// the two to keep them in sync.
	BrowserFS.configure({
		fs: "AsyncMirror",
		options: {
			sync: {
				fs: "InMemory"
			},
			async: {
				fs: "Dropbox",
				options: {
					client: dropboxClient
				}
			}
		}
	}, cb);
}
function setupBFS() {
	// Grab the BrowserFS Emscripten FS plugin.
	var BFS = new BrowserFS.EmscriptenFS();
	// Create the folder that we'll turn into a mount point.
	FS.createFolder(FS.root, 'data', true, true);
	// Mount BFS's root folder into the '/data' folder.
	FS.mount(BFS, {root: '/'}, '/data');
}

Testing

To run unit tests, simply run npm test.

Citing

BrowserFS is a component of the Doppio and Browsix research projects from the PLASMA lab at the University of Massachusetts Amherst. If you decide to use BrowserFS in a project that leads to a publication, please cite the academic papers on Doppio and Browsix:

John Vilk and Emery D. Berger. Doppio: Breaking the Browser Language Barrier. In Proceedings of the 35th ACM SIGPLAN Conference on Programming Language Design and Implementation (2014), pp. 508–518.

@inproceedings{VilkDoppio,
	author		= {John Vilk and
							 Emery D. Berger},
	title		 = {{Doppio: Breaking the Browser Language Barrier}},
	booktitle = {Proceedings of the 35th {ACM} {SIGPLAN} Conference on Programming Language Design and Implementation},
	pages		 = {508--518},
	year			= {2014},
	url			 = {http://doi.acm.org/10.1145/2594291.2594293},
	doi			 = {10.1145/2594291.2594293}
}

Bobby Powers, John Vilk, and Emery D. Berger. Browsix: Bridging the Gap Between Unix and the Browser. In Proceedings of the Twenty-Second International Conference on Architectural Support for Programming Languages and Operating Systems (2017), pp. 253–266.

@inproceedings{PowersBrowsix,
	author		= {Bobby Powers and
							 John Vilk and
							 Emery D. Berger},
	title		 = {{Browsix: Bridging the Gap Between Unix and the Browser}},
	booktitle = {Proceedings of the Twenty-Second International Conference on Architectural
							 Support for Programming Languages and Operating Systems},
	pages		 = {253--266},
	year			= {2017},
	url			 = {http://doi.acm.org/10.1145/3037697.3037727},
	doi			 = {10.1145/3037697.3037727}
}

License

BrowserFS is licensed under the MIT License. See LICENSE for details.