wsfs

wsfs starts a WebSocket server (ws) that broadcasts file system (fs) events to its clients. It is implemented in TypeScript for Deno.

deno.land mod deno.land doc tag MIT license CI Code coverage

Motivation

For developing websites or web-based applications, it can sometimes be useful if one can use the web-browser to access information from a file system. For example, an automatic reload can be triggered when source files change, or a file listing can be updated when new files are added in a cloud storage app. There is no native API that allows a web-browser to watch a file system. wsfs implements a protocol for collecting and broadcasting that information to clients. Building on the WebSocket protocol further guarantees that updates can be delivered quickly and frequently.

Scenarios

  • You are developing a website in a source code editor. In order to see the changes, you have to manually reload the website in the web-browser. By running wsfs in the directory and listening to the WebSocket server in a <script> element, automatic reloads can be triggered after every change.
  • You are deploying a web app that allows users to upload files to a shared folder. The users have to reload the file listing to see whether another user has changed the contents of the folder. By running wsfs on the server users can be notified automatically.

Documentation

wsfs comes with a command-line interface defined in cli.ts and the underlying TypeScript interface defined in mod.ts. The latter can be used for integrating wsfs into TypeScript applications.

cli.ts

The CLI serves as (1) a convenient way of using wsfs in practice, and (2) as an application example for mod.ts. Usage and installation instructions can be printed in a terminal with deno:

deno run https://deno.land/x/wsfs/cli.ts --help

mod.ts

The Server function returns a Server object. If successful, it starts two processes: (1) the WebSocket server and (2) the file watcher. Both can be shut down with the Server.close function:

import { Server } from "https://deno.land/x/wsfs/mod.ts";

// Start server.
const server: Server = Server();

// Print server URL.
console.log(server.url);

// Shut down the server at some point.
await server.close();

An Options object can be specified to configure the server. All entries are optional:

import { Event, Options } from "https://deno.land/x/wsfs/mod.ts";

const options: Options = {
  // Default settings for starting the server at: ws://localhost:1234
  hostname: "localhost",
  port: 1234,

  // Specify the path to observe.
  path: "some/path",

  // Handle server events.
  handle: (e: Event) => console.log(e),
};

const server = Server(options);
await server.close();

That’s it!