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JavaScript track
Exercises
Exercises on the JavaScript track
Join the JavaScript Track
106 exercises to help you master JavaScript
easy
Hello World
The classical introductory exercise. Just say "Hello, World!"
optional values
strings
text formatting
conditionals
easy
Two Fer
Create a sentence of the form "One for X, one for me."
optional values
strings
text formatting
easy
Resistor Color
Convert a resistor band's color to its numeric representation
arrays
strings
easy
Resistor Color Duo
Convert color codes, as used on resistors, to a numeric value.
strings
arrays
easy
Gigasecond
Given a moment, determine the moment that would be after a gigasecond has passed.
time
easy
RNA Transcription
Given a DNA strand, return its RNA Complement Transcription.
strings
transforming
easy
Space Age
Given an age in seconds, calculate how old someone is in terms of a given planet's solar years.
floating point numbers
easy
Pangram
Determine if a sentence is a pangram.
algorithms
lists
maps
searching
strings
conditionals
loops
easy
Bank Account
Simulate a bank account supporting opening/closing, withdraws, and deposits of money. Watch out for concurrent transactions!
classes
conditionals
easy
Matrix
Given a string representing a matrix of numbers, return the rows and columns of that matrix.
arrays
matrices
text formatting
conditionals
loops
medium
Bob
Bob is a lackadaisical teenager. In conversation, his responses are very limited.
pattern recognition
regular expressions
strings
conditionals
polymorphism
medium
Pascal's Triangle
Compute Pascal's triangle up to a given number of rows.
strings
text formatting
math
conditionals
loops
medium
Linked List
Implement a doubly linked list
algorithms
arrays
lists
optional values
conditionals
loops
data structures
medium
Grade School
Given students' names along with the grade that they are in, create a roster for the school
arrays
maps
sorting
medium
List Ops
Implement basic list operations
lists
recursion
loops
data structures
medium
Robot Name
Manage robot factory settings.
exception handling
randomness
regular expressions
sets
conditionals
medium
Simple Cipher
Implement a simple shift cipher like Caesar and a more secure substitution cipher
algorithms
randomness
strings
text formatting
transforming
conditionals
loops
medium
Wordy
Parse and evaluate simple math word problems returning the answer as an integer.
exception handling
parsing
pattern recognition
regular expressions
strings
conditionals
loops
medium
Secret Handshake
Given a decimal number, convert it to the appropriate sequence of events for a secret handshake.
algorithms
arrays
bitwise operations
games
conditionals
loops
easy
Leap
Given a year, report if it is a leap year.
booleans
integers
logic
easy
Reverse String
Reverse a string
loops
strings
easy
Collatz Conjecture
Calculate the number of steps to reach 1 using the Collatz conjecture
exception handling
integers
recursion
math
conditionals
loops
easy
Triangle
Determine if a triangle is equilateral, isosceles, or scalene.
exception handling
integers
conditionals
loops
medium
Clock
Implement a clock that handles times without dates.
dates
globalization
time
medium
Meetup
Calculate the date of meetups.
dates
equality
exception handling
time
conditionals
loops
easy
ETL
We are going to do the `Transform` step of an Extract-Transform-Load.
integers
maps
transforming
loops
easy
Hamming
Calculate the Hamming difference between two DNA strands.
equality
strings
conditionals
loops
easy
Raindrops
Convert a number to a string, the content of which depends on the number's factors.
integers
strings
transforming
conditionals
medium
Nucleotide Count
Given a DNA string, compute how many times each nucleotide occurs in the string.
arrays
strings
text formatting
conditionals
loops
medium
Scrabble Score
Given a word, compute the Scrabble score for that word.
maps
strings
conditionals
loops
medium
Allergies
Given a person's allergy score, determine whether or not they're allergic to a given item, and their full list of allergies.
arrays
bitwise operations
conditionals
loops
easy
Word Count
Given a phrase, count the occurrences of each word in that phrase.
lists
regular expressions
strings
loops
easy
Difference Of Squares
Find the difference between the square of the sum and the sum of the squares of the first N natural numbers.
algorithms
integers
math
loops
easy
Perfect Numbers
Determine if a number is perfect, abundant, or deficient based on Nicomachus' (60 - 120 CE) classification scheme for positive integers.
arrays
integers
math
conditionals
loops
medium
Complex Numbers
Implement complex numbers.
math
medium
Luhn
Given a number determine whether or not it is valid per the Luhn formula.
integers
strings
conditionals
loops
medium
Prime Factors
Compute the prime factors of a given natural number.
algorithms
integers
math
conditionals
loops
medium
Grains
Calculate the number of grains of wheat on a chessboard given that the number on each square doubles.
integers
loops
medium
Pythagorean Triplet
There exists exactly one Pythagorean triplet for which a + b + c = 1000. Find the product a * b * c.
algorithms
integers
math
conditionals
loops
medium
Palindrome Products
Detect palindrome products in a given range.
algorithms
exception handling
integers
math
conditionals
loops
easy
Anagram
Given a word and a list of possible anagrams, select the correct sublist.
filtering
strings
easy
Acronym
Convert a long phrase to its acronym
regular expressions
strings
transforming
loops
easy
High Scores
Manage a player's High Score list
arrays
easy
Isogram
Determine if a word or phrase is an isogram.
filtering
strings
easy
Matching Brackets
Make sure the brackets and braces all match.
exception handling
parsing
strings
conditionals
loops
easy
Phone Number
Clean up user-entered phone numbers so that they can be sent SMS messages.
parsing
transforming
easy
Series
Given a string of digits, output all the contiguous substrings of length `n` in that string.
exception handling
strings
text formatting
loops
medium
Largest Series Product
Given a string of digits, calculate the largest product for a contiguous substring of digits of length n.
exception handling
integers
regular expressions
strings
math
conditionals
loops
easy
Transpose
Take input text and output it transposed.
arrays
lists
loops
matrices
strings
text formatting
medium
Rectangles
Count the rectangles in an ASCII diagram.
arrays
matrices
strings
conditionals
loops
medium
Spiral Matrix
Given the size, return a square matrix of numbers in spiral order.
arrays
matrices
conditionals
loops
data structures
medium
OCR Numbers
Given a 3 x 4 grid of pipes, underscores, and spaces, determine which number is represented, or whether it is garbled.
equality
exception handling
integers
parsing
text formatting
conditionals
loops
medium
Saddle Points
Detect saddle points in a matrix.
equality
exception handling
integers
matrices
optional values
parsing
conditionals
loops
hard
Forth
Implement an evaluator for a very simple subset of Forth
domain specific languages
parsing
stacks
medium
Food Chain
Generate the lyrics of the song 'I Know an Old Lady Who Swallowed a Fly'
algorithms
text formatting
medium
House
Output the nursery rhyme 'This is the House that Jack Built'.
arrays
recursion
strings
conditionals
loops
medium
ISBN Verifier
Check if a given string is a valid ISBN-10 number.
pattern recognition
regular expressions
conditionals
loops
medium
Pig Latin
Implement a program that translates from English to Pig Latin
games
regular expressions
strings
transforming
conditionals
loops
medium
Proverb
For want of a horseshoe nail, a kingdom was lost, or so the saying goes. Output the full text of this proverbial rhyme.
arrays
optional values
strings
text formatting
conditionals
loops
medium
Twelve Days
Output the lyrics to 'The Twelve Days of Christmas'
pattern recognition
regular expressions
strings
conditionals
loops
polymorphism
medium
Beer Song
Produce the lyrics to that beloved classic, that field-trip favorite: 99 Bottles of Beer on the Wall.
strings
conditionals
loops
medium
Resistor Color Trio
Convert color codes, as used on resistors, to a human-readable label.
conditionals
loops
medium
Say
Given a number from 0 to 999,999,999,999, spell out that number in English.
exception handling
integers
strings
text formatting
conditionals
loops
medium
Diamond
Given a letter, print a diamond starting with 'A' with the supplied letter at the widest point.
arrays
exception handling
games
parsing
text formatting
conditionals
loops
medium
Rational Numbers
Implement rational numbers.
algorithms
floating point numbers
math
medium
Sublist
Write a function to determine if a list is a sublist of another list.
arrays
lists
medium
Binary Search Tree
Insert and search for numbers in a binary tree.
algorithms
recursion
conditionals
loops
medium
Custom Set
Create a custom set type.
arrays
equality
lists
recursion
sets
conditionals
loops
data structures
medium
Binary Search
Implement a binary search algorithm.
algorithms
arrays
recursion
conditionals
loops
hard
Circular Buffer
A data structure that uses a single, fixed-size buffer as if it were connected end-to-end.
arrays
exception handling
lists
conditionals
loops
data structures
hard
Simple Linked List
Write a simple linked list implementation that uses Elements and a List
arrays
lists
data structures
hard
Word Search
Create a program to solve a word search puzzle.
arrays
equality
optional values
parsing
text formatting
conditionals
loops
medium
Variable Length Quantity
Implement variable length quantity encoding and decoding.
bitwise operations
transforming
medium
Two Bucket
Given two buckets of different size, demonstrate how to measure an exact number of liters.
algorithms
arrays
exception handling
games
parsing
conditionals
loops
medium
Alphametics
Write a function to solve alphametics puzzles.
algorithms
games
easy
Scale Generator
Generate musical scales, given a starting note and a set of intervals.
loops
pattern recognition
strings
arrays
medium
Connect
Compute the result for a game of Hex / Polygon
arrays
games
maps
parsing
conditionals
loops
hard
Bowling
Score a bowling game
arrays
exception handling
games
parsing
text formatting
conditionals
loops
medium
Strain
Implement the `keep` and `discard` operation on collections. Given a collection and a predicate on the collection's elements, `keep` returns a new collection containing those elements where the predicate is true, while `discard` returns a new collection containing those elements where the predicate is false.
algorithms
arrays
callbacks
filtering
lists
conditionals
loops
medium
Accumulate
Implement the `accumulate` operation, which, given a collection and an operation to perform on each element of the collection, returns a new collection containing the result of applying that operation to each element of the input collection.
algorithms
callbacks
lists
loops
medium
Flatten Array
Take a nested list and return a single list with all values except nil/null
arrays
recursion
medium
Nth Prime
Given a number n, determine what the nth prime is.
algorithms
exception handling
integers
math
conditionals
loops
medium
Sieve
Use the Sieve of Eratosthenes to find all the primes from 2 up to a given number.
integers
recursion
math
conditionals
loops
easy
Rotational Cipher
Create an implementation of the rotational cipher, also sometimes called the Caesar cipher.
strings
text formatting
transforming
conditionals
easy
Diffie Hellman
Diffie-Hellman key exchange.
algorithms
arrays
exception handling
math
conditionals
loops
medium
Affine Cipher
Create an implementation of the Affine cipher, an ancient encryption algorithm from the Middle East.
algorithms
arrays
filtering
math
medium
Atbash Cipher
Create an implementation of the atbash cipher, an ancient encryption system created in the Middle East.
algorithms
arrays
regular expressions
text formatting
conditionals
loops
hard
Crypto Square
Implement the classic method for composing secret messages called a square code.
algorithms
arrays
regular expressions
sorting
text formatting
transforming
conditionals
loops
medium
Robot Simulator
Write a robot simulator.
exception handling
games
parsing
strings
conditionals
loops
medium
Kindergarten Garden
Given a diagram, determine which plants each child in the kindergarten class is responsible for.
arrays
strings
text formatting
conditionals
loops
medium
Sum Of Multiples
Given a number, find the sum of all the multiples of particular numbers up to but not including that number.
integers
lists
math
conditionals
loops
hard
Change
Correctly determine change to be given using the least number of coins
algorithms
performance
searching
easy
Protein Translation
Translate RNA sequences into proteins.
algorithms
strings
conditionals
loops
easy
Armstrong Numbers
Determine if a number is an Armstrong number
algorithms
math
easy
Run Length Encoding
Implement run-length encoding and decoding.
exception handling
parsing
pattern recognition
regular expressions
strings
text formatting
conditionals
easy
Darts
Write a function that returns the earned points in a single toss of a Darts game
misc
easy
Roman Numerals
Write a function to convert from normal numbers to Roman Numerals.
pattern recognition
transforming
conditionals
loops
medium
All Your Base
Convert a number, represented as a sequence of digits in one base, to any other base.
exception handling
integers
parsing
math
conditionals
loops
medium
Minesweeper
Add the numbers to a minesweeper board
algorithms
arrays
games
hard
Queen Attack
Given the position of two queens on a chess board, indicate whether or not they are positioned so that they can attack each other.
equality
exception handling
optional values
parsing
text formatting
conditionals
loops
hard
React
Implement a basic reactive system.
algorithms
events
reactive programming
hard
Zipper
Creating a zipper for a binary tree.
recursion
searching
trees
easy
D&D Character
Randomly generate Dungeons & Dragons characters
classes
randomness
medium
Grep
Search a file for lines matching a regular expression pattern. Return the line number and contents of each matching line.
files
searching
text formatting
medium
Yacht
Score a single throw of dice in the game Yacht
arrays
conditionals
filtering
games
medium
Dominoes
Make a chain of dominoes.
graph theory