Codewars · JavaScript

JavaScript katas on Codewars are programming challenges that help you improve your skills in the language. Each kata presents a specific problem for you to solve using programming techniques and algorithms. Upon completing each kata, you can compare your solution with others and receive feedback and points based on its effectiveness and efficiency.

Table of contents
4 kyu 5 kyu 6 kyu 7 kyu 8 kyu

4 kyu

• Binary multiple of 3
  ^{REGULAR EXPRESSIONS ALGORITHMS PUZZLES NUMBER THEORY}
• Human readable duration format
  ^{STRINGS DATE TIME ALGORITHMS}
• Most frequently used words in a text
  ^{STRINGS FILTERING ALGORITHMS REGULAR EXPRESSIONS}
• Snail
  ^{ARRAYS ALGORITHMS}

5 kyu

• By the Power Set of Castle Grayskull
  ^{MATHEMATICS ALGORITHMS}
• Convert A Hex String To RGB
  ^{PARSING STRINGS ALGORITHMS}
• Convert PascalCase string into snake_case
  ^{STRINGS ALGORITHMS}
• Don't Drink the Water
  ^{ALGORITHMS ARRAYS SORTING LISTS}
• Extract the domain name from a URL
  ^{PARSING REGULAR EXPRESSIONS}
• First non-repeating character
  ^{STRINGS ALGORITHMS}
• Greed is Good
  ^ALGORITHMS
• Human Readable Time
  ^{DATE TIME MATHEMATICS ALGORITHMS}
• Josephus Survivor
  ^{MATHEMATICS COMBINATORICS ALGORITHMS LISTS ARRAYS}
• Maximum subarray sum
  ^{ALGORITHMS LISTS DYNAMIC PROGRAMMING FUNDAMENTALS PERFORMANCE}
• Mean Square Error
  ^{ARRAYS MATHEMATICS ALGORITHMS}
• Moving Zeros To The End
  ^{ARRAYS SORTING ALGORITHMS}
• Not very secure
  ^{REGULAR EXPRESSIONS STRINGS}
• Number of trailing zeros of N!
  ^{ALGORITHMS LOGIC MATHEMATICS}
• Perimeter of squares in a rectangle
  ^{MATHEMATICS ALGORITHMS}
• Pete, the baker
  ^ALGORITHMS
• Regex Password Validation
  ^{REGULAR EXPRESSIONS FUNDAMENTALS}
• RGB To Hex Conversion
  ^ALGORITHMS
• ROT13
  ^{STRINGS CIPHERS REGULAR EXPRESSIONS ALGORITHMS}
• Rot13
  ^{CIPHERS FUNDAMENTALS}
• Scramblies
  ^{STRINGS PERFORMANCE ALGORITHMS}
• Simple Fun #249: Subtraction By Regrouping
  ^PUZZLES
• Simple Pig Latin
  ^{REGULAR EXPRESSIONS ALGORITHMS}
• String incrementer
  ^{REGULAR EXPRESSIONS STRINGS}
• The Hashtag Generator
  ^{STRINGS ALGORITHMS}
• Tic-Tac-Toe Checker
  ^{ARRAYS ALGORITHMS}
• Value of x
  ^{STRINGS ALGORITHMS}
• Weight for weight
  ^ALGORITHMS
• Where my anagrams at?
  ^{STRINGS ALGORITHMS}

6 kyu

• Are they the "same"?
  ^FUNDAMENTALS
• Array Helpers
  ^{ARRAYS FUNDAMENTALS}
• Array.diff
  ^{ARRAYS FUNDAMENTALS ALGORITHMS}
• ASCII Fun #1: X-Shape
  ^{ASCII ART}
• ASCII Fun #2: Funny Dots
  ^{ASCII ART}
• ASCII Fun #3: Puzzle Tiles
  ^{ASCII ART}
• ASCII Fun #4: Build a pyramid
  ^{ASCII ART}
• Bit Counting
  ^{BITS ALGORITHMS}
• Break camelCase
  ^{STRINGS FUNDAMENTALS}
• Build a pile of Cubes
  ^{MATHEMATICS ALGORITHMS}
• Build Tower!
  ^{STRINGS ASCII ART FUNDAMENTALS}
• CamelCase Method
  ^{FUNDAMENTALS ALGORITHMS STRINGS}
• Card game
  ^{ALGORITHMS GAMES STRINGS}
• Checkered Board
  ^{STRINGS ASCII ART FUNDAMENTALS}
• Clever split
  ^{STRINGS REGULAR EXPRESSIONS FUNDAMENTALS}
• Collatz
  ^{NUMBER THEORY ALGORITHMS}
• Consecutive strings
  ^FUNDAMENTALS
• Convert string to camel case
  ^{REGULAR EXPRESSIONS ALGORITHMS STRINGS}
• Count characters in your string
  ^{STRINGS FUNDAMENTALS}
• Count the smiley faces!
  ^{REGULAR EXPRESSIONS FUNDAMENTALS}
• Counting Duplicates
  ^{STRINGS FUNDAMENTALS}
• Create Phone Number
  ^{ARRAYS STRINGS REGULAR EXPRESSIONS ALGORITHMS}
• Data Reverse
  ^{ARRAYS FUNDAMENTALS}
• Decode the Morse code
  ^ALGORITHMS
• Delete occurrences of an element if it occurs more than n times
  ^{LISTS FUNDAMENTALS}
• Detect Pangram
  ^{STRINGS DATA STRUCTURES FUNDAMENTALS}
• Does my number look big in this?
  ^ALGORITHMS
• Duplicate Encoder
  ^ALGORITHMS
• Emotional Sort ( ︶︿︶)
  ^{ARRAYS FUNDAMENTALS SORTING}
• Extract the IDs from the data set
  ^{ARRAYS ALGORITHMS}
• Find Cracker.
  ^{FUNDAMENTALS ARRAYS}
• Find the missing letter
  ^{MATHEMATICS ALGORITHMS}
• Find the odd int
  ^FUNDAMENTALS
• Find The Parity Outlier
  ^ALGORITHMS
• Find the unique number
  ^{FUNDAMENTALS ALGORITHMS ARRAYS}
• Good vs Evil
  ^ALGORITHMS
• Handshake problem
  ^ALGORITHMS
• Highest Scoring Word
  ^{FUNDAMENTALS STRINGS ARRAYS}
• IP Validation
  ^{REGULAR EXPRESSIONS ALGORITHMS}
• Is a number prime?
  ^{MATHEMATICS ALGORITHMS}
• Make the Deadfish Swim
  ^{PARSING ALGORITHMS}
• Matrix Addition
  ^{MATRIX ARRAYS ALGORITHMS}
• Meeting
  ^FUNDAMENTALS
• Mexican Wave
  ^{ARRAYS STRINGS FUNDAMENTALS}
• Multiples of 3 or 5
  ^{MATHEMATICS ALGORITHMS}
• Multiplication table
  ^{ARRAYS FUNDAMENTALS}
• Number Format
  ^{REGULAR EXPRESSIONS FUNDAMENTALS}
• Persistent Bugger
  ^FUNDAMENTALS
• Piano Kata, Part 1
  ^FUNDAMENTALS
• Piano Kata, Part 2
  ^FUNDAMENTALS
• Playing with digits
  ^{FUNDAMENTALS MATHEMATICS}
• Prefill an Array
  ^{ARRAYS FUNDAMENTALS}
• Replace With Alphabet Position
  ^{STRINGS FUNDAMENTALS}
• Roman Numerals Encoder
  ^ALGORITHMS
• Selective Array Reversing
  ^{ALGORITHMS LOGIC ARRAYS}
• Simple Fun #212: Processing Requests!
  ^FUNDAMENTALS
• Sort My Animals
  ^{LISTS SORTING FUNDAMENTALS}
• Sort the odd
  ^{FUNDAMENTALS ARRAYS SORTING}
• Split Strings
  ^{REGULAR EXPRESSIONS STRINGS ALGORITHMS}
• Stop gninnipS My sdroW!
  ^{STRINGS ALGORITHMS}
• Sum of Digits / Digital Root
  ^{MATHEMATICS ALGORITHMS}
• Sums of Parts
  ^{FUNDAMENTALS PERFORMANCE ALGORITHMS}
• Take a Number And Sum Its Digits Raised To The Consecutive Powers And ....¡Eureka!!
  ^{FUNDAMENTALS MATHEMATICS}
• Take a Ten Minutes Walk
  ^{ARRAYS FUNDAMENTALS}
• The Deaf Rats of Hamelin
  ^{FUNDAMENTALS STRINGS ALGORITHMS QUEUES DATA STRUCTURES}
• The Office V - Find a Chair
  ^{FUNDAMENTALS ARRAYS STRINGS}
• The Supermarket Queue
  ^{ARRAYS FUNDAMENTALS}
• Title Case
  ^{STRINGS FUNDAMENTALS}
• Tombola - validation
  ^{ARRAYS FUNDAMENTALS}
• Triangle of Multiples (Easy One)
  ^{MATHEMATICS DATA STRUCTURES FUNDAMENTALS}
• Tribonacci Sequence
  ^{NUMBER THEORY ARRAYS LISTS FUNDAMENTALS}
• Two Sum
  ^{ARRAYS FUNDAMENTALS ALGORITHMS}
• Unique In Order
  ^{ALGORITHMS FUNDAMENTALS}
• Valid Braces
  ^ALGORITHMS
• Valid Parentheses
  ^ALGORITHMS
• Valid Phone Number
  ^{REGULAR EXPRESSIONS ALGORITHMS}
• WeIrD StRiNg CaSe
  ^{STRINGS ALGORITHMS}
• What century is it?
  ^{STRINGS ALGORITHMS DATE TIME}
• Which are in?
  ^{ARRAYS LISTS STRINGS REFACTORING}
• Who likes it?
  ^{STRINGS FUNDAMENTALS}
• Write Number in Expanded Form
  ^{STRINGS MATHEMATICS ALGORITHMS FUNDAMENTALS}
• Your order, please
  ^{STRINGS FUNDAMENTALS}
• Zero-plentiful Array
  ^FUNDAMENTALS
• Ziiiiip!
  ^{ARRAYS FUNDAMENTALS}

7 kyu

• Alphabetical Addition
  ^ALGORITHMS
• Anagram Detection
  ^{STRINGS FUNDAMENTALS}
• Area of an arrow
  ^MATHEMATICS
• Array2Binary addition
  ^FUNDAMENTALS
• Beginner Series #3 Sum of Numbers
  ^{FUNDAMENTALS ALGORITHMS}
• Binary Addition
  ^{BINARY FUNDAMENTALS}
• Complementary DNA
  ^{STRINGS FUNDAMENTALS}
• Converting 12-hour time to 24-hour time
  ^{DATE TIME ALGORITHMS}
• Count the divisors of a number
  ^{NUMBER THEORY MATHEMATICS FUNDAMENTALS}
• Credit Card Mask
  ^{STRINGS ALGORITHMS}
• Descending Order
  ^FUNDAMENTALS
• Digit*Digit
  ^{MATHEMATICS FUNDAMENTALS}
• Disemvowel Trolls
  ^{STRINGS REGULAR EXPRESSIONS FUNDAMENTALS}
• Every possible sum of two digits
  ^ALGORITHMS
• Exes and Ohs
  ^FUNDAMENTALS
• Factorial
  ^FUNDAMENTALS
• Find Count of Most Frequent Item in an Array
  ^{DATA STRUCTURES FUNDAMENTALS}
• Find missing numbers
  ^{ARRAYS FUNDAMENTALS}
• Find the capitals
  ^{STRINGS ARRAYS FUNDAMENTALS}
• Find the divisors!
  ^{MATHEMATICS ALGORITHMS}
• Find The Duplicated Number in a Consecutive Unsorted List
  ^{ARRAYS ALGORITHMS}
• Find the middle element
  ^{ARRAYS FUNDAMENTALS}
• Find the next perfect square!
  ^{ALGEBRA FUNDAMENTALS}
• Find the stray number
  ^{FUNDAMENTALS ALGORITHMS}
• Fix string case
  ^FUNDAMENTALS
• Friend or Foe?
  ^FUNDAMENTALS
• Get key/value pairs as arrays
  ^{ARRAYS FUNDAMENTALS}
• Get the Middle Character
  ^{FUNDAMENTALS STRINGS}
• Highest and Lowest
  ^{FUNDAMENTALS STRINGS}
• Homogenous arrays
  ^{ARRAYS FUNDAMENTALS FUNCTIONAL PROGRAMMING}
• How many e-mails we sent today?
  ^{FUNDAMENTALS LOGIC MATHEMATICS}
• Is n divisible by (...)?
  ^FUNDAMENTALS
• Is this a triangle
  ^{MATHEMATICS FUNDAMENTALS}
• isAN(value)
  ^FUNDAMENTALS
• isEven? - Bitwise Series
  ^{RESTRICTED FUNDAMENTALS}
• Isograms
  ^{STRINGS FUNDAMENTALS}
• Jaden Casing Strings
  ^{STRINGS FUNDAMENTALS}
• L2: Triple X
  ^{STRINGS REGULAR EXPRESSIONS FUNDAMENTALS}
• Leap Years
  ^{DATE TIME ALGORITHMS}
• Letterbox Paint-Squad
  ^FUNDAMENTALS
• List Filtering
  ^{LISTS FILTERING DATA STRUCTURES FUNDAMENTALS}
• Make a function that does arithmetic!
  ^FUNDAMENTALS
• Matrix creation
  ^{FUNDAMENTALS ARRAYS MATRIX LINEAR ALGEBRA MATHEMATICS LANGUAGE FEATURES}
• Merge two arrays
  ^{FUNDAMENTALS ARRAYS}
• Mumbling
  ^{FUNDAMENTALS STRINGS PUZZLES}
• Naughty or Nice?
  ^{MATHEMATICS FUNDAMENTALS}
• Naughty or Nice
  ^{JSON FUNDAMENTALS}
• Number of People in the Bus
  ^FUNDAMENTALS
• Odd Not Prime
  ^ALGORITHMS
• Odd or Even?
  ^{FUNDAMENTALS ARRAYS}
• Ones and Zeros
  ^{FUNDAMENTALS ARRAYS}
• Only one
  ^ALGORITHMS
• Plus - minus - plus - plus - ... - Count
  ^FUNDAMENTALS
• Printer Errors
  ^FUNDAMENTALS
• Regex validate PIN code
  ^{REGULAR EXPRESSIONS FUNDAMENTALS}
• Remove anchor from URL
  ^{REGULAR EXPRESSIONS STRINGS FUNDAMENTALS}
• Remove the minimum
  ^{LISTS ARRAYS FUNDAMENTALS}
• Return the closest number multiple of 10
  ^{MATHEMATICS FUNDAMENTALS}
• Reverse words
  ^{STRINGS FUNDAMENTALS}
• Round up to the next multiple of 5
  ^FUNDAMENTALS
• Shortest Word
  ^FUNDAMENTALS
• Simple Fun #181: Rounding
  ^FUNDAMENTALS
• Small enough? - Beginner
  ^{FUNDAMENTALS ARRAYS}
• Sort array by string length
  ^{SORTING ARRAYS FUNDAMENTALS}
• Sort Numbers
  ^FUNDAMENTALS
• Sorted Union
  ^{ARRAYS LISTS ALGORITHMS SORTING}
• String ends with?
  ^{STRINGS FUNDAMENTALS}
• Sum of odd numbers
  ^{ARRAYS LISTS MATHEMATICS FUNDAMENTALS}
• Sum of the first nth term of Series
  ^FUNDAMENTALS
• Sum of two lowest positive integers
  ^{ARRAYS FUNDAMENTALS}
• Tail Swap
  ^FUNDAMENTALS
• Testing 1-2-3
  ^{ARRAYS FUNDAMENTALS}
• The highest profit wins!
  ^{LISTS ARRAYS FUNDAMENTALS}
• The Office I - Outed
  ^{FUNDAMENTALS ARRAYS}
• The Office II - Boredom Score
  ^{ARRAYS FUNDAMENTALS}
• The Office III - Broken Photocopier
  ^{FUNDAMENTALS STRINGS ARRAYS}
• The Office IV - Find a Meeting Room
  ^{FUNDAMENTALS ARRAYS}
• Two to One
  ^FUNDAMENTALS
• V A P O R C O D E
  ^{STRINGS FUNDAMENTALS}
• Vowel Count
  ^{STRINGS FUNDAMENTALS}
• You're a square!
  ^{FUNDAMENTALS MATHEMATICS}

8 kyu

• Chuck Norris VII - True or False? (Beginner)
  ^{FUNDAMENTALS ALGORITHMS}
• Compare within margin
  ^{FUNDAMENTALS LOGIC}
• Convert a Number to a String!
  ^{STRINGS FUNDAMENTALS}
• Convert a string to an array
  ^{ARRAYS STRINGS FUNDAMENTALS}
• Convert boolean values to strings 'Yes' or 'No'.
  ^FUNDAMENTALS
• Even or Odd
  ^{MATHEMATICS FUNDAMENTALS}
• Formatting decimal places #0
  ^FUNDAMENTALS
• Is your period late?
  ^{FUNDAMENTALS DATE TIME}
• Multiplication table for number
  ^{FUNDAMENTALS STRINGS}
• Multiply
  ^{DEBUGGING FUNDAMENTALS}
• Not so black box
  ^PUZZLES
• OOP: Object Oriented Piracy
  ^{OBJECT-ORIENTED PROGRAMMING FUNDAMENTALS}
• Opposites Attract
  ^FUNDAMENTALS
• Power
  ^RESTRICTED
• Remove First and Last Character Part Two
  ^{FUNDAMENTALS ARRAYS STRINGS}
• Removing Elements
  ^{LISTS ARRAYS FUNDAMENTALS}
• Return Negative
  ^FUNDAMENTALS
• Reversed Strings
  ^{STRINGS FUNDAMENTALS}
• Simple Comparison?
  ^{FUNDAMENTALS STRINGS}
• Sum of positive
  ^{ARRAYS FUNDAMENTALS}