Analyse and edit binary files wherever you want, on any operating system, whether on a desktop or smartphone, and without installing any software. All you need is a modern web browser (Mozilla Firefox 53+, Google Chrome 58+, Opera 44+, Apple Safari 11+, Microsoft Edge 20+).

The complete file processing is done by your browser and HTML5 functionality. HexEd.it does not upload your data to the server. It can also compute various hash functions.

HexEd.it has a small memory footprint - it does not keep your files in memory. This makes it possible to handle very large files even on low-RAM machines. HexEd.it has been tested on files as large as 150 GiB.

See also https://jsqr.de/ for a QR-encoder.

Found on https://www.hpmuseum.org/forum/thread-18335-post-159984.html#pid159984

Found on the FSF website https://www.fsf.org/news/fsf-announces-jshelter-browser-add-on-to-combat-threats-from-nonfree-javascript
As of 2022-01-05, it can be installed on Firefox, Chrome and Opera.

emacs-ng is based off of the master branch of emacs, and regularly merges in the latest changes(this branch includes the native compilation feature from Andrea Corallo).

This project should be considered an additive native layer over emacs, bringing features like Deno's Javascript and Async I/O environment, Mozilla's Webrender, and other features in development. emacs-ng's approach is to utilize multiple new development approaches and tools to bring Emacs to the next level. It is maintained by a team that loves Emacs and everything it stands for - being totally introspectable, with a fully customizable and free development environment. We want Emacs to be a editor 40+ years from now that has the flexibility and design to keep up with progressive technology.

tufte.js is a D3 based library.

WARNING: PROBABLY INSECURE
This is a version of drawterm (a program for connecting to Plan 9 systems) which runs in a webbrowser. To connect to the remote host, it uses Websockets, which means you need a proxy such as websockify.

Jsdrawterm is written in Javascript, but it uses a bunch of C libraries from Plan 9 (for crypto and drawing routines) which need to be compiled to Webassembly. Since the Javascript also deals with some of the crypto, it's probably horribly insecure and hackers will steal your cats.

Simulator and assembler for pdp-11, written in JavaScript.

Klipse https://github.com/viebel/klipse
allows to interactively edit and run programs written in
Common Lisp, javascript, clojure[script], python, brainfuck, scheme
in a Javascript-enabled web browser.
Ironically, it does not seem to work with Firefox 52.6.0 (64-bit)/Windows 7.

Another pdp-11 simulator written in Javascript.

WaveDrom draws your Timing Diagram or Waveform from simple textual description.
It comes with description language, rendering engine and the editor.
WaveDrom editor works in the browser or can be installed on your system.
Rendering engine can be embeded into any webpage.

Calendar generator http://www.jgae.de/kalender.htm
Self-decrypting archive http://www.jgae.de/sda.htm (symmetric en/decryption in Javascript).