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A collection of command-line tools for developing JS1K submissions.
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JS1K Development Harness

A collection of command-line tools for developing JS1K entries.


npm install -g js1k-harness


git clone git://
cd js1k-harness
npm link


Run the js1k executable. It provides three main subcommands:

js1k init

Creates a boilerplate js file that you can add your entry's code to.

js1k serve

Starts a web server that serves your entry inside the js1k shim. This will automatically minify your code for you (with uglify-js), and show the current size of your entry in the browser. It reloads and minifies your javascript on every request, so you don't need to restart the server when your code changes (just refresh your browser).

js1k build

Dumps your minified entry code to the console. You can submit this directly to js1k, although you can probably still save a couple more bytes by editing the output manually (removing var, etc).

Full command list (js1k -h)

Usage: js1k [options] [command]


  init                   Create a new js1k boilerplate javascript file
  serve                  Serve your minified js in the js1k shim (on port 3001)
  build                  Outputs a minified version of your javascript, suitable for submission
  rules                  Open the js1k rules page
  submit                 Open the js1k submission page


  -h, --help     output usage information
  -V, --version  output the version number


The byte savings you get from uglify-js can take you a long way, but beyond that there are a lot of clever manual tricks to slim your entry down even further. These articles have some great tips:

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