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Cover image for Vanilla JavaScript palindrome checker in 3 lines

Vanilla JavaScript palindrome checker in 3 lines

dailydevtips1 profile image Chris Bongers Originally published at daily-dev-tips.com ・2 min read

There comes a time in your life where you need a palindrome checker!

You might now think, what is a palindrome?

It's a word or sentence like mom that you can reverse, and it's still mom!

If that time comes, think about this article and how to check for palindromes in JavaScript.

We will be building this amazing palindrome function, try it out on my Codepen. (See console logs!)

JavaScript palindrome function

To create our function we define a function that accepts one argument, a string.

function palindrome(string) {
    // Code here
}
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Then we need to convert our input string to lowercase and remove all whitespace.

const original = string.replace(/\s/g,'').toLowerCase();
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We are using a regular expression to remove all whitespaces.

The next step is to get the reverse of our string.
We we split every character and reverse the array, then we rejoin that array in reversed order.

const reverse = original.split('').reverse().join('');
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The last step is to check if they are equal.

return original === reverse;
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The whole function will look like this.

function palindrome(string) {
  const original = string.replace(/\s/g,'').toLowerCase();
  const reverse = original.split('').reverse().join('');
  return original === reverse;
}
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Awesome, let's see how it works in action.

console.log(palindrome('Mom')); // True
console.log(palindrome('A nut for a jar of tuna')); // True
console.log(palindrome('Not a palindrome')); // False
console.log(palindrome('Taco cat')); // True
console.log(palindrome('Yo banana boy')); // True
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Great stuff, we now have a palindrome checker in JavaScript!

Thank you for reading, and let's connect!

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Discussion

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alekseiberezkin profile image
Aleksei Berezkin

Nice trick! Because string is iterable, you may also reverse with:

[...original].reverse().join('')
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dailydevtips1 profile image
Chris Bongers Author

Yes absolutely right there!

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aakatev profile image
Artem

why i love js, that you can fit it all in one liner 😂 😂 😂

let palindrome = (string) =>
  string.replace(/\s/g, "").toLowerCase() ===
  string.replace(/\s/g, "").toLowerCase().split("").reverse().join("")
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mrwebuzb profile image
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dailydevtips1 profile image
Chris Bongers Author

True haha!
Need to add this as well, just wanted the exploded view for people to understand

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toanoop profile image
Anoop Sivadas

const checkPalin = words => words.split('').reverse().toString() === words.split('').toString()?'The word is a palindrome':'The Word is not a palindrome';

in a single line .....

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dailydevtips1 profile image
Chris Bongers Author

Yes nice one Anoop, was mentioned above as well, I just like to showcase the code more readable for new people 🤟