Explore the JavaScript exercises on Exercism

Exercism's classic introductory exercise. Just say "Hello, World!".

Learn the basics of JavaScript cooking a brilliant lasagna from your favorite cooking book.

Help Annalyn free her best friend using boolean logic in JavaScript

Learn about numbers whilst helping a freelancer communicate with a project manager about day- and month rates.

Learn about strings using poems to get into the poetry club.

Help Elyse with her Enchantments and learn about arrays in the process.

Learn about comparison and conditionals while preparing for your next vehicle purchase

Professionalize counting the birds in your garden with for loops and increment/decrement operators

Help your friend Li Mei run her juice bar with your knowledge of while loops and switch statements.

Practice type conversion while helping your friend Kojo with his website www.fun-with-numbers.com.

Elyse's magic training continues, teaching you about useful built-in methods to analyse arrays.

Elyse's magic training continues, teaching you about array destructing and the rest/spread operator.

Sift through Elyse's array of cards using various looping methods.

Learn about undefined and null by managing visitors and tickets at an amusement park.

Allow customers to calculate the cost of their order

Practice your knowledge of closures by implementing various coordinate transformations.

Learn about callbacks ordering fruit from the grocer

Connect to the Klingon Translation Service and learn about promises.

Practice JavaScript objects by tracking high scores of an arcade game.

Use sets to avoid repeating tracks in a playlist

Dive deeper into JavaScript functions while preparing to cook the perfect lasagna.

Learn how to handle errors by creating a piece of software for a newspaper factory.

Elyse has grown her magical powers and attempts some really cool tricks now while you learn about transforming arrays.

Learn about template strings and the ternary operator ...

Learn about prototypes and classes by developing a windowing system.

Learn the basics of regular expressions with JavaScript by helping a chatbot understand humans.

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

Convert a resistor band's color to its numeric representation.

Convert color codes, as used on resistors, to a numeric value.

Given a moment, determine the moment that would be after a gigasecond has passed.

Given a DNA strand, return its RNA Complement Transcription.

Given an age in seconds, calculate how old someone is in terms of a given planet's solar years.

Determine if a sentence is a pangram.

Given a string representing a matrix of numbers, return the rows and columns of that matrix.

Bob is a lackadaisical teenager. In conversation, his responses are very limited.

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.

Compute Pascal's triangle up to a given number of rows.

Implement a doubly linked list.

Given students' names along with the grade that they are in, create a roster for the school.

Implement basic list operations.

Manage robot factory settings.

Implement a simple shift cipher like Caesar and a more secure substitution cipher.

Parse and evaluate simple math word problems returning the answer as an integer.

Given a decimal number, convert it to the appropriate sequence of events for a secret handshake.

Determine whether a given year is a leap year.

Reverse a given string.

Calculate the number of steps to reach 1 using the Collatz conjecture.

Determine if a triangle is equilateral, isosceles, or scalene.

Implement a clock that handles times without dates.

Calculate the date of meetups.

Change the data format for scoring a game to more easily add other languages.

Calculate the Hamming distance between two DNA strands.

Convert a number into its corresponding raindrop sounds - Pling, Plang and Plong.

Given a DNA string, compute how many times each nucleotide occurs in the string.

Given a word, compute the Scrabble score for that word.

Given a person's allergy score, determine whether or not they're allergic to a given item, and their full list of allergies.

Given a phrase, count the occurrences of each word in that phrase.

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

Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.

Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60 - 120 CE) classification scheme for positive integers.

Implement complex numbers.

Given a number determine whether or not it is valid per the Luhn formula.

Compute the prime factors of a given natural number.

Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.

Given an integer N, find all Pythagorean triplets for which a + b + c = N.

Detect palindrome products in a given range.

Given a word and a list of possible anagrams, select the correct sublist.

Convert a long phrase to its acronym.

Manage a player's High Score list.

Determine if a word or phrase is an isogram.

Make sure the brackets and braces all match.

Clean up user-entered phone numbers so that they can be sent SMS messages.

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

Given a string of digits, output all the contiguous substrings of length `n` in that string.

Given a string of digits, calculate the largest product for a contiguous substring of digits of length n.

Take input text and output it transposed.

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

Count the rectangles in an ASCII diagram.

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

Given a 3 x 4 grid of pipes, underscores, and spaces, determine which number is represented, or whether it is garbled.

Detect saddle points in a matrix.

Implement an evaluator for a very simple subset of Forth.

Generate the lyrics of the song 'I Know an Old Lady Who Swallowed a Fly'.

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

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

Implement a program that translates from English to Pig Latin.

For want of a horseshoe nail, a kingdom was lost, or so the saying goes. Output the full text of this proverbial rhyme.

Output the lyrics to 'The Twelve Days of Christmas'.

Practice promises by implementing some common promise functions.

Score a single throw of dice in the game Yacht.

Convert color codes, as used on resistors, to a human-readable label.

Make a chain of dominoes.

Given a number from 0 to 999,999,999,999, spell out that number in English.

Given a letter, print a diamond starting with 'A' with the supplied letter at the widest point.

Implement rational numbers.

Write a function to determine if a list is a sublist of another list.

Insert and search for numbers in a binary tree.

Create a custom set type.

Implement a binary search algorithm.

A data structure that uses a single, fixed-size buffer as if it were connected end-to-end.

Write a simple linked list implementation that uses Elements and a List.

Create a program to solve a word search puzzle.

Implement variable length quantity encoding and decoding.

Given two buckets of different size, demonstrate how to measure an exact number of liters.

Given an alphametics puzzle, find the correct solution.

Compute the result for a game of Hex / Polygon.

Score a bowling game.

Implement the `keep` and `discard` operation on collections.

Take a nested list and return a single list with all values except nil/null.

Given a number n, determine what the nth prime is.

Use the Sieve of Eratosthenes to find all the primes from 2 up to a given number.

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

Diffie-Hellman key exchange.

Create an implementation of the Affine cipher, an ancient encryption algorithm from the Middle East.

Create an implementation of the Atbash cipher, an ancient encryption system created in the Middle East.

Implement the classic method for composing secret messages called a square code.

Write a robot simulator.

Given a diagram, determine which plants each child in the kindergarten class is responsible for.

Given a number, find the sum of all the multiples of particular numbers up to but not including that number.

Correctly determine change to be given using the least number of coins.

Translate RNA sequences into proteins.

Determine if a number is an Armstrong number.

Randomly generate Dungeons & Dragons characters.

Implement run-length encoding and decoding.

Calculate the points scored in a single toss of a Darts game.

Convert modern Arabic numbers into Roman numerals.

Given a natural radicand, return its square root.

Convert a number, represented as a sequence of digits in one base, to any other base.

Add the numbers to a minesweeper board.

Given the position of two queens on a chess board, indicate whether or not they are positioned so that they can attack each other.

Implement a basic reactive system.

Creating a zipper for a binary tree.

Solve the zebra puzzle.

Tally the results of a small football competition.

Implement encoding and decoding for the rail fence cipher.

Implement a RESTful API for tracking IOUs.

Count the scored points on a Go board.

Given a knapsack that can only carry a certain weight, determine which items to put in the knapsack in order to maximize their combined value.

Rebuild binary trees from pre-order and in-order traversals.

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

Help Eliud count the number of eggs in her chicken coop by counting the number of 1 bits in a binary representation.

Count the frequency of letters in texts using parallel computation.

Produce the lyrics to the popular children's repetitive song: Ten Green Bottles.

Refactor a Markdown parser.

Given an input string, truncate it to 5 characters.

Refactor a ledger printer.

Determine the game state of a match of Tic-Tac-Toe.

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

Write a tool that makes it easier to solve Killer Sudokus