Evan Hahn's projects

The highlights:

Signal: a messaging app that puts privacy first. I made many contributions to the open source iOS and desktop apps.
Helmet helps secure Express.js web apps by setting HTTP response headers. Adam Baldwin created the project and I took over as the primary maintainer in 2013. I’ve learned a lot along the way. The project was downloaded over 158 million times in 2024.
Express in Action: a book I wrote about Express.js and its ecosystem. Published in 2016 so it’s a little outdated, but I’m proud of it.
HumanizeDuration.js turns milliseconds into duration strings. For example, it turns 361,000 milliseconds into “6 minutes, 1 second”. Dozens of contributors have localized it into 58 different languages.
dotfiles are how I configure my Linux and macOS machines. I’ve been maintaining this repository for a long time and wrote some reflections about it.

Writing

I’ve written many guides, tutorials, and how-tos. Two of those got turned into books:

Express.js in Action, a Manning book
JavaScript Testing with Jasmine, an O’Reilly book

In addition, here are a few blog posts I’m especially proud of:

If you’re a Legend of Zelda fan, you can also find my writing over at Zelda Dungeon.

Jobs

I’ve worked at:

Awana Digital builds software to help frontline communities defend their environmental and human rights. I primarily worked on CoMapeo, a peer-to-peer mapping and monitoring app that helps Indigenous people protect their land. I worked on the tool’s “plumbing”, which included work on a complex sync system, peer discovery, and privacy-respecting metrics.
Signal is a non-profit encrypted messenger used by millions around the world. I worked on the iOS and Desktop apps. I built many things including an encrypted group calling feature, a privacy-preserving donations feature, and much more.
Airtable is a tool to organize anything. I was on the Platform team where I worked on the REST API, Extensions (formerly known as Apps and Blocks), and much more. I learned a ton about programming, prioritization, product, and puppies.
Braintree lets developers easily accept payments. I was on the Contextual Commerce (now called Extend) team where I did a lot of Clojure and Ruby. Before that, I spent a lot of time building Braintree’s SDKs. My biggest project was Hosted Fields, a fancy way to accept credit cards on a webpage. We even got a patent for it, which I have mixed feelings about.

I’ve also done some part-time work for Rec on their authentication and payment systems, Sensaphonics with a web-based firmware updater, Codecademy with their “Learn React” course, Cooler with their climate change API, and Kanary with their matching infrastructure.

Before graduating college, I had a few other part-time jobs, mostly internships:

Counsyl, now Myriad Genetics, aimed to give everybody “access to vital information about their bodies to help them confidently make choices about their lives”. They did this by doing complicated genetic tests and presenting them to patients in accessible ways. I wrote a lot of Django and Python code for them, and even programmed a small robot! One of the coolest parts of the internship was seeing all of the people in white lab coats, something I will likely never wear. Fun fact: they were my third internship in a row that had a nearly-boundless supply of string cheese.
Sencha provides frameworks for building cross-platform applications. They had me working on their Sencha Architect team. Architect describes itself as a “visual app builder”, and I’d describe it as a huge, powerful JavaScript application that I helped to work on. I learned a bunch about Ext JS and Sencha Touch, and spent a few weeks deep in Node.js as well.
UniversityNow provided affordable, accredited online higher education. The first weeks of my internship were fixing bugs and implementing small features in Rails, but then I spent the rest of the summer working on their real-time chat feature. I learned Backbone.js and wrote a whole lot of Jasmine specs.
Fetchnotes was a note-taking app that aims to be “your mind’s best friend”. Their homepage and web app got a redesign by a brilliant designer, and I coded them both up! I bumbled my way through Ember.js to make it work. Soon after, a TechCrunch story was written and it got tens of thousands of hits! And it worked! Scary stuff. The service is no longer around.
Rockmelt was acquired by Yahoo awhile after I left. While I was there, they built a social browser; a fork of Google Chrome that baked things like Facebook and Twitter right into the browser. I worked on some internal help pages. Designers gave me PNGs and I gave them their “Quick Guide”! I also did some other pages for them (such as their What’s New page or some fixes on their homepage) and a lot of internal JavaScript unit tests.

Full list of projects

A wallpaper from a NASA photo
America’s DJ was a Twitter bot that tweets fake DJ names pulled from US military operations. You can find the source here.
American police shooting countdown, my entry to JS1024 2020
arraywrap.js wraps an element in an array if it isn’t one already
backbone-getnset adds custom getters and setters to Backbone.js models
Bits Required implements “how many bits do we need to represent integer X?” in various languages
Brainfuck interpreter, in Python
Brainfuck syntax highlighting for Atom
Brainfuck web app, a simple web app written in Brainfuck
BRAINFUCK2000, a powerful JavaScript Brainfuck interpreter for the stars
BREACH helper for Node helps to mitigate BREACH attacks by adding a random-length HTML comment helper
BrowserIs asks questions about Node.js requests useragents. Made for Express
C program to repeat a string forever
Caesar shift in JavaScript and CoffeeScript
Canvas to favicon sends a <canvas> to the favicon
Check ECMAScript Version Compatibility checks that your JavaScript is compatible with the right version of ECMAScript
ChicagoCTA is a Mastodon bot that tweets alerts from Chicago public transit
ChiPy Mentorship Program had me as a mentor in the Fall 2017 cohort
Circles 1K is 639 bytes of trippy and was an entry to JS1k
ClimateAction.tech community support
Close the popups was my entry to JS1k 2019
coinflip.js randomly returns true or false
connect-appcache adds Appcache middleware to Connect/Express
Content Security Policy sandbox is a little test app for playing around with Content Security Policy
context.clear is a small library for clearing a HTML5 canvas
Crystal PNG chunks offers low-level access to PNG chunk data
Custom Steam icons for Zineth, Lode Runner 2
cyborg.txt is a collection of robots.txt utilities for Node
Deep Proxy uses JavaScript proxies to allow deep property access
document.head shim for CommonJS
Dragon Scales was my entry for JS1k 2014
dw_red.vim is a red-heavy Vim colorscheme
Euler Method calculator in C++
Evan Hahn’s 100 dope beats of the day
EvanSpec is a souped-up assert for C++
Expecting.js is an assertion module for JavaScript
Facebook autopoker Chrome extension (or the source)
ffmpeg buddy helps you build ffmpeg commands
Fireworks was my entry to JS1k 2016
FLoC Block is a small Express middleware to block Google’s FLoC tracking
Flood is a game I didn’t invent but did implement. A friend didn’t like the version she was playing, so I made one that she liked
Fudo is an adorable friend that was made from scratch in 36 hours at a hackathon. Art by Lulu Tang. Sound and code help from David Jackson
functional state machine is a small JavaScript state machine that’s purely functional
get the latest Node version from Node
Gopher Node lets you write Gopher servers with Node
Gribbagrab is an asynchronous JavaScript and CSS loader that’s meant to be inlined
haha.sh is a simple shell script that generates hearty laughter
Helmet for Crystal is a collection of security handlers for the Crystal programming language
Helmet is a collection of security middlewares for Express
Hide the Facebook news feed
How many English words are alphabetical?
HTML Pack inlines CSS and JavaScript for an HTML page and then minifies everything
HumanizeDuration.js turns milliseconds into English durations, or many other languages
image to table converts images to all-HTML <table> tags
Internet Creator, my entry to JS1024 2022
Is GitHub Up? is a command-line tool that tells you if GitHub is online
iscp is an interactive scp, because I always forget the syntax
isExpress is a function for detecting Express applications
ISO 3166 country list maps things like “DE” to “Germany” and vice-versa
JavaScript Jabber episode 311: “Securing Express Apps with Helmet.js with Evan Hahn”
JavaScript/CoffeeScript sleepsort
journ is a command-line journal
JSCPP is a shoddy attempt to port some of JavaScript’s standard library to C++
JSTypes is a small JavaScript library that deals with variable types
Legend of Zelda: Tears of the Kingdom prerelease roundups (as of April 2023, as of February 2023, as of January 2023, as of December 2022, as of November 2022, as of September 2022, as of August 2022, as of May 2022, as of April 2022, as of March 2022, as of December 2021)
Light Switch is a 2032-byte black cat, submitted to the Taper zine
Lil’ pages is a collection of little web-based utilities
Link’s Awakening.txt is a Mastodon bot that periodically posts text from The Legend of Zelda: Link’s Awakening
Lucky Picross, my entry to JS1024 ‘23. Won third place!
luhncheck is a little website that runs a number through a Luhn validator
mailtolink.js creates mailto: links from JavaScript
map-invert inverts JavaScript Maps
map-omit removes keys from JavaScript Maps
Meme.js is a canvas-based meme generator I worked on for now-defunct Buddy Meme
MiniClass is yet another JavaScript library that allows for simple classical OO. It’s tiny
minidots are a couple of dotfiles I use when SSHing or in VMs
MouseTracker.js creates an object called mouse and keeps its x and y properties updated
Naps and their effectiveness
nimi mute is a dictionary for the Toki Pona mini-language
Node Hyperdrive import is an experimental Node module that lets you import packages from Hyperdrive
Node torrent import is an experimental Node module that lets you import packages from BitTorrent. See my accompanying blog post
NONOGRAM NIGHTS is a spooky puzzle where you use logic to uncover a mysterious picture
Origin won 7th place in the 2013 js13kgames. I also wrote a little blog post about it
Paint the box, my entry to JS1024 2021
Percentage.js is a simple function to convert numbers to percentages, like 0.12 to 12%
Persisted JSON objects are plain JavaScript objects that save themselves to the file system after every change
Pie Time was my entry to JS1k 2015. I also wrote a post about it
Pinboard to Standard Notes Importer moves Pinboard bookmarks into Standard Notes. See the source code
Playback speed calculator tells you that listening to a 4 hour audiobook on 1.5× speed will take 2 hours, 40 minutes. I also wrote a post about this
PNG Chunk Editor lets you edit the bytes that make up a PNG image, and I made it in an hour
PNG Chunk Explorer lets you explore the bytes that make up a PNG image
Potions was my entry to JS1k 2017
Predicting the next Zelda’s release date based on historical data
Proof of concept: drop-in JSON replacement that produces smaller payloads
Pushbullet CLI is a command-line interface to Pushbullet. I’m no longer the maintainer
pwgen is a little webpage for generating passwords
python -m json.tool for JavaScript emulates Python’s json.tool in pure JavaScript
QR It turns text into QR
random-word is a CLI tool to pick a random word from a file
Reddit’s /r/dailyprogrammer challenge solutions
Remember The Milk script to estimate selected tasks
Remember The Milk script to export tasks as CSV
Remember The Milk script to find tasks with invalid start times
Remember The Milk script to get task permalink
rename is an interactive version of the mv command
ring-secure-headers adds security HTTP headers to Ring apps (for Clojure)
RTS camera for Unity is a little utility for RTS games in Unity. Made it for a university course
scrabbler is a small Scrabble cheater written in Python
ScriptInclude adds include to browser-based JavaScript and is tiny
setBigTimeout is an answer to the fact that setTimeout doesn’t work for 1 million years
setAttributes helps you call .setAttribute on a DOM node more easily
Simple Statistics is a Crystal shard for simple statistical operations, such as median or standard deviation
Single Color Image lets you generate a PNG that’s just one color. It’s a simple app with a simple API
SnackWrap allows you to watch files and run a shell command every time a file changes. Not as focused as Grunt or Sprockets
startInterval is like JavaScript’s setInterval but it starts immediately. It was made for a guide
string-timing-safe-equal, a Node package for comparing strings in a way that’s safe against timing attacks
Study guides from my time as an undergraduate at the University of Michigan: semester 3, semester 4, semester 5, and semester 6
Sqids Crystal is a port of the Sqids serialization format to Crystal
The TypeScript Grunt skeleton
Tic Tac Toe in Lua
Ticker is a lightweight wrapper around requestAnimationFrame
Time in Korea is a simple Android app that tells you the time in South Korea
tiny “coming soon” page
TinyTar is a tiny library (376 bytes gzipped) for creating tar files
toki pona to hex converts the Toki Pona language to and from hex
Truth table generator for CoffeeScript. Made to take the tedium out of a homework assignment
Try EJS
Try LiScript
Two’s complement utility for converting from two’s complement numbers
Two-factor authentication list
untouched gets pristine copies of built-in objects (like Array or JSON) even if they’ve been modified
User Agent Bag parses user agents per RFC7231
UTF-21 is a toy character encoding like UTF-8
VimL syntax highlighting for Atom
What if the English language had syntax highlighting?
when-file-exists calls a callback when a file is created
wren-please is an assertion library for Wren
wren-vector is a 3D vector library for Wren
XML to text turns XML to plain text with Python
Zap was my entry to JS1k 2018. It was an honorable mention—read my post about it
ZoomContext lets you pan and zoom around an HTML5 canvas

Open source contributions

A big list of open source projects I’ve contributed to but don’t run myself.