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Based on Edgecase's fantastic Ruby koans, the goal of the Javascript koans is to teach you Javascript programming through testing.

When you first run the koans, you'll be presented with a runtime error and a stack trace indicating where the error occurred. Your goal is to make the error go away. As you fix each error, you should learn something about the Javascript language and functional programming in general.

Your journey towards Javascript enlightenment starts in the koans/AboutExpects.js file. These koans will be very simple, so don't overthink them! As you progress through more koans, more and more Javascript syntax will be introduced which will allow you to solve more complicated problems and use more advanced techniques.

Running the Koans

Simply navigate to the Javascript Koans folder using a file browser, and double click on KoansRunnner.html.

Any browser will do, but for the best results Firefox or Chrome is recommended. More stack trace information shows up for javascript on these browsers.

The first error will be in koans/AboutExpects.js. Fix the first test and refresh the browser. Rinse and repeat until all tests turn green.

The test runner used is Jasmine with a customized report viewer.


  • v3 - Nov 2010 - Moved out of branch of functional-koans project, into own top level project
  • v2 - Sept 2010 - Second version based on jasmine (Thanks Greg Malcolm!)
  • v1 - July 2010 - First version based on jsTestDriver


  • Dick Wall (the Java posse) - for bringing the idea of koans to my attention
  • Edgecase - for the great Ruby Koans
  • Douglas Crockford - for Javascript; the good bits

MIT Licensed