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.

Provided backends:

• XmlHttpRequest (downloads files on-demand from a webserver)
• localStorage
• HTML5 FileSystem
• Dropbox
• In-memory
• Zip file-backed FS (currently read only)

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

For more information, see the wiki.

Building

Prerequisites:

• Node and NPM
• Grunt-CLI and Bower globally installed: npm install -g grunt-cli bower
• Run npm install to install local dependencies

Release:

grunt

The minified release build can be found in lib/browserfs.js.

Development:

grunt dev

The development build can be found as multiple AMD modules in tmp.

Custom builds:

If you want to build BrowserFS with a subset of the available backends, remove unwanted backends listed in Gruntfile.js under the include property of the compile task, and remove the require statements for unwanted backends in build/outro.js. Then, perform a release build.

Using

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

<script type="text/javascript" src="browserfs.js"></script>
<script type="text/javascript">
  // Installs globals onto window:
  // * Buffer
  // * require (monkey-patches if already defined)
  // * process
  // You can pass in an arbitrary object if you do not wish to pollute
  // the global namespace.
  BrowserFS.install(window);
  // Constructs an instance of the LocalStorage-backed file system.
  var lsfs = new BrowserFS.FileSystem.LocalStorage();
  // Initialize it as the root file system.
  BrowserFS.initialize(lsfs);
</script>

Now, you can write code like this:

var fs = require('fs');
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());
  });
});

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.js into the page, and add code similar to the following to your Module's preRun array:

/**
 * Mounts a localStorage-backed file system into the /home folder of Emscripten's file system.
 */
function setupBFS() {
  // Constructs an instance of the LocalStorage-backed file system.
  var lsfs = new BrowserFS.FileSystem.LocalStorage();
  // Initialize it as the root file system.
  BrowserFS.initialize(lsfs);
  // 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, 'home', true, true);
  // Mount BFS's root folder into the '/home' folder.
  FS.mount(BFS, {root: '/'}, '/home');
}

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.

Testing

Prerequisites:

• Karma globally installed: npm install -g karma

To run unit tests, simply run grunt test (NOTE: This will launch multiple web browsers!). You may need to change build/karma.conf.js if you do not have Chrome, Safari, Opera, and Firefox installed.

License

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