Add new JavaScript exercises

One of the easiest ways to add new exercises to the JavaScript track is to translate them from other language tracks on Exercism. This page lists all of the problem specifications in the common pool of exercises which have not yet been implemented in JavaScript.

The icon links to the language-independent description of the problem.

The icon links to the canonical test data.

We also link to all the implementations of each exercise in other languages, which you can use for inspiration.

Once you've picked an exercise, follow the instructions in this guide and submit your pull request to the JavaScript track repository on GitHub.




Rotational Cipher

Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.

Bank Account

Simulate a bank account supporting opening/closing, withdraws, and deposits of money. Watch out for concurrent transactions!

Two Fer

Create a sentence of the form "One for X, one for me."


Implement an evaluator for a very simple subset of Forth


Implement a basic reactive system.


Output the nursery rhyme 'This is the House that Jack Built'.


Tally the results of a small football competition.


Compute the result for a game of Hex / Polygon


Pick the best hand(s) from a list of poker hands.


Make a chain of dominoes.

Parallel Letter Frequency

Count the frequency of letters in texts using parallel computation.

Variable Length Quantity

Implement variable length quantity encoding and decoding.


Creating a zipper for a binary tree.

Book Store

To try and encourage more sales of different books from a popular 5 book series, a bookshop has decided to offer discounts of multiple-book purchases.

Complex Numbers

Implement complex numbers.

Rail Fence Cipher

Implement encoding and decoding for the rail fence cipher.

Spiral Matrix

Given the size, return a square matrix of numbers in spiral order.

Word Search

Create a program to solve a word search puzzle.


Refactor a Markdown parser


Reparent a graph on a selected node


Count the rectangles in an ASCII diagram.


Search a file for lines matching a regular expression pattern. Return the line number and contents of each matching line.

Scale Generator

Generate musical scales, given a starting note and a set of intervals.

Zebra Puzzle

Solve the zebra puzzle.

Error Handling

Implement various kinds of error handling and resource management

Sgf Parsing

Parsing a Smart Game Format string.

Dot Dsl

Write a Domain Specific Language similar to the Graphviz dot language

Go Counting

Count the scored points on a Go board.


Implement the logic of the hangman game using functional reactive programming.


Refactor a ledger printer.

Lens Person

Use lenses to update nested records (specific to languages with immutable data).

Tree Building

Refactor a tree building algorithm.


Report network IO statistics

Isbn Verifier

Check if a given string is a valid ISBN-10 number.