Check If A String Is A Palindrome in JS

In this article, I'll be teaching you how to check if a string is a palindrome in JavaScript.

Lets start off by describing what a palindrome actually is.

What Is A Palindrome?

A palindrome a word that reads the same backwards as forwards. Pretty simple right? You've probably heard of words like racecar and level which are both palindromes because when you read them backwards, they spell the exam same word.

How To Check If A String Is A Palindrome

In layman's terms, to check if a string is a palindrome, we have to reverse it and check if the reverse is equal to the original. To actually code this, lets write a simple JavaScript function that takes in a str parameter and returns a Boolean that signifies whether the passed in str is a palindrome or not.

Lets call this function checkPalindrome:

const checkPalindrome = str => {
    // Return Boolean
}

Firstly, we will reverse the string. To reverse the string, we will first split it into an array, reverse the array and then join it back into a string. We can use the .split, .reverse and .join methods respectively:

const checkPalindrome = str => {
    let reversedStr = str.split("").reverse().join("");
}

The empty quotes ("") passed into the split and join methods means it will split each letter separately and not add a space when joining them back together.

We can then return reversedStr == str which return true if its a palindrome and false if its not:

const checkPalindrome = str => {
    let reversedStr = str.split("").reverse().join("");
    return reversedStr == str;
}

We now have a working checkPalindrome function that if you test with a word like racecar will work.

One problem is that if a single letter in the word is uppercase, it will return false since its case-sensitive. We can fix this bug by converting both strings (reversed and original) to lowercase:

const checkPalindrome = str => {
    let reversedStr = str.split("").reverse().join("");
    return reversedStr.toLowerCase() == str.toLowerCase();
}

Done! 😀

Take Away

You've now learned how to check if a string is a palindrome in JavaScript. This solution is very simple, however it doesn't take into account punctuation and whitespace. Both of which would lead to more steps in the solution.

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Check If A String Is A Palindrome in JS

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