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JavaScript Katas: Is it a palindrome?

July, 2020

Intro 🌐

Problem solving is an important skill, for your career and your life in general.

That’s why I take interesting katas of all levels, customize them and explain how to solve them.


Understanding the Exercise❗

First, we need to understand the exercise! If you don’t understand it, you can’t solve it!.

My personal method:

  1. Input: What do I put in?
  2. Output: What do I want to get out?

Today’s exercise

Source: Codewars

Write a function isPalindrome, that accepts one parameter: myString.

Given a string, e.g. "Abba", return if this string is a palindrome (case-insensitive), e.g. true.

A palindrome is a word […] which reads the same backward as forward, such as racecar.


Input: a string.

Output: a boolean.


Thinking about the Solution 💭

I think I understand the exercise (= what I put into the function and what I want to get out of it).

Now, I need the specific steps to get from input to output.

I try to do this in small baby steps:

  1. Transform the input string to lowercase
  2. Get the backward version of the lowercase string (= reverse it)
  3. Check if the forward string is the same as the backward string

Example:

  • Input: "Abba"
  • Transform the input string to lowercase: "abba"
  • Get the backward version of the lowercase string: "abba"
  • Check if the forward string is the same as the backward string: true
  • Output: true

Implementation ⛑

function isPalindrome(myString) {
  // transform the input string to lowercase
  const lowercaseInput = myString.toLowerCase();

  // to have a similar wording
  const forward = lowercaseInput;

  // get the backward version of the lowercase string
  const backward = lowercaseInput.split("").reverse().join("");

  // check if the forward string is the same as the backward string
  return forward === backward;
}

Result

console.log(isPalindrome("Abba"));
// true ✅

console.log(isPalindrome("hello"));
// false ✅

Playground ⚽

You can play around with the code here


Next Part ➡️

Great work!

We learned how to use toLowerCase, split, reverse, join.

I hope you can use your new learnings to solve problems more easily!

Next time, we’ll solve another interesting kata. Stay tuned!


If I should solve a specific kata, shoot me a message here.

If you want to read my latest stuff, get in touch with me!


Further Reading 📖


Questions ❔

  • How often do you do katas?
  • Which implementation do you like more? Why?
  • Any alternative solution?

miku86

Hi! I'm Michael 👋 I'm a Mentor & Educator & Senior Web Developer - I help you to reach your (career) goals.