Skip to content
A ClojureScript adaptation of the Clojure koans that runs purely in-browser
Clojure HTML CSS Ruby Shell JavaScript
Find file
Latest commit 133058d @lazerwalker Merge pull request #9 from orthographic-pedant/spell_check/accommodate
Fixed typographical error, changed accomodate to accommodate in README.

ClojureScript Koans Online

The ClojureScript Koans are a fun and easy way to get started with ClojureScript. No experience with Clojure or ClojureScript is assumed or required, and since they're run in-browser they don't require a functioning Clojure development environment.

They are adapted from the Clojure Koans, with some minor changes to accommodate the differences between Clojure and ClojureScript.

Unlike most other browser-based ClojureScript evaluation environments, the ClojureScript Koans don't require a connection to a server-side REPL. Rather, they are run in a purely in-browser REPL powered by @kanaka's cljs-in-cljs project. This means that they are nothing more than static HTML, CSS, and ClojureScript files.


You will need both Leiningen and a functioning copy of the cljs-in-cljs version of the cljsc compiler in your PATH. For instructions on installing cljs-in-cljs, see

If you wish to edit the project's stylesheets, you will need to have Sass and Compass installed. The project contains a Compass config.rb file.

Editing the Koans

The koans themselves live in the src/koans/meditations folder. For a given set, the koans variable should contain a sequence of description strings and their matching S-expressions. Within the S-expressions, any instances of :__ will be replaced by an input box. There are instances where ClojureScript's pr-str function will alter the displayed form of an expression (e.g. replacing quote characters with a (quote) expression); if this happens, you can quote the entire S-expression to have it displayed exactly as written.

If you need to define new functions for a section, add them to the fns vector. Like the koans, a function may either be a quoted S-expression or a string, and any instances of the symbol :__ will be replaced with an input field. If you wish to specify proper indentation, whitespace is maintained in the string form. In either case, syntax highlighting will automatically be applied.

If you want to create a new category of koans, you will also need to add your category to the structure in meditations.cljs.

Helper Scripts

The script folder contains a number of helpful scripts. All are designed to be run from the root project directory.

build-repl: Recompiles just the REPL core using cljs-in-cljs.

build: Recompiles the REPL core, and does a clean recompile of the application code.

deploy: If you're hosting the site on GitHub Pages, this will deploy the latest version of your code. It merges your current branch into the gh-pages branch, generates a static copy with compiled JS/CSS, and then pushes the gh-pages branch to your default remote. See the script's source for caveats.


Pull requests are encouraged!


The use and distribution terms for this software are covered by the Eclipse Public License 1.0 ( which can be found in the file epl-v10.html at the root of this distribution. By using this software in any fashion, you are agreeing to be bound by the terms of this license.

Something went wrong with that request. Please try again.