Building a Palindrome Checker using Split, Join and replace methods

amarachukwu profile image Amarachi Emmanuela Azubuike Updated on ・2 min read

So, recently I embarked on building the projects on the FreeCodeCamp JavaScript course, and I've decided to write about the steps I took to build them out as I proceed.

So, first, I created a palindrome identifier- a function that can be able to figure out if a word is a palindrome irrespective of whether it has non-alphanumeric characters or spaces.

First, what is a palindrome?

Palindrome are words or sentences that spelled the same way both forward and backward, ignoring punctuation, case, and spacing, this means that the words are exactly the same even when they are turned upside down. For instance, the word eye looks the same even when turned both ways.

So, in the next few minutes, you'll be building along with me a function that returns true if a word is palindrome and false if it's not, ignoring spaces and non-alphanumeric characters.


Before we proceed, you should have a knowledge of the following JavaScript methods:
If you don't have an idea, take few minutes to read up this articles on split , reverse, replace and join methods.

Getting Started

Let's write our algorithm

  1. Remove spaces and alphanumeric characters from the string and store in a variable
  2. Reverse the string and also store in a variable.
  3. Compare the string and the reversed string
  4. Return true if they are same and false if they are not equal

Let write our code

First,we'll define our function. Our function will be taking a string str as argument

function palindrome(str){


Secondly, we have to eliminate spaces and alphanumeric characters from the string. We'll be using regex for this.
We'll also convert the word to lowercase. You can choose to change yours to uppercase
The aim of this is to keep all the alphabets on the same case to ease comparison.

function palindrome(str) {
let palindrom=str.replace(/[^0-9a-z]/gi, '').toLowerCase();


Having done this, let's create another variable reversed where we'll store the reversed string. (We'll be reversing the variable palindrom above)

function palindrome(str) {
let palindrom=str.replace(/[^0-9a-z]/gi, '').toLowerCase();
let reversed=palindrom.split("").reverse().join('');


Let's compare

function palindrome(str) {
let palindrom=str.replace(/[^0-9a-z]/gi, '').toLowerCase();
let reversed=palindrom.split("").reverse().join('');

    return true;
  }else return false;


Quite a short one, but yeah, we have a function here which can detect palindromes.

I'd love to entertain feedback from you. Thanks for reading.

Posted on by:

amarachukwu profile

Amarachi Emmanuela Azubuike


I am a front-end web developer, interested in teaching and learning.


markdown guide

You could simplify the return statement like this:

function isPalindrome(str) {
    const palindrome = str.replace(/[^0-9a-z]/gi, '').toLowerCase();

    return palindrome.split('').reverse().join('') === palindrome;

Oh! Thanks. This is a lot more simplified and brief


Very cool!

Every time I think of palindromes, I think of this Weird Al spoof on Bob Dylan's Subterranean Homesick Blues:


The video isn't available in my country. Thanks for sharing though


Dang! If you decided you want to check it out, just search for Weird Al Yankovic - "Bob" ... it's a spoof on a song by Bob Dylan called "Subterranean Homesick Blues" but every verse is a palindrome.

const palindrome=s=>[...s.replace(/[\W_]/gi,'').toLowerCase()].reverse().join('')==s