How to Check String is Palindrome in JavaScript

1. Palindrome in JavaScript With Built-in Functions
2. Palindrome in JavaScript With for Loop

A palindrome is a word, number, phrase, or other sequence of characters that can be read backward and forwards, like adida or racecar. There are also numeric palindromes, including date and time stamps using short digits.

For example, 11 November 2011 is considered a palindrome day 111111 using the dd-mm-yy format as it can be read from left to right or vice versa. Sentence-length palindromes ignore punctuation, capitalization, and word boundaries.

This article teaches us to check if string/number is a palindrome in JavaScript.

Palindrome in JavaScript With Built-in Functions

JavaScript provides several functions that we can use to detect whether a string is a palindrome or not.

1. First, convert the string into an array using the string.split() function.

   The split() method is a built-in method provided by JavaScript. This method splits the string into a list of substrings.

   This cut is performed by taking the separator as an input.

   This separator is purely an optional input. And based on that, all these substrings are placed in an array, and the array is returned.

   You can also pass limit as input to the method, limiting the number of substrings in the array.

2. Second, use the reverse() method to reverse the array’s values.

   The reverse() method is a built-in method provided by JavaScript. This method reverses an original array instead.

   The first element of an array becomes the last element of an array, and the array’s last element becomes the first element.

3. Last, use the join() method to group values of the array into the string.

   The join() method is a built-in method provided by JavaScript. This method creates and returns a new string by concatenating all the elements in an array (or array-like object), separated by commas or a specified delimiter string.

   If the array has only one element, that element is returned without using the delimiter.

Let’s combine all the above methods and check if the input string is a palindrome.

function palindromeFn(inputString) {
  return inputString == inputString.split('').reverse().join('');
}
console.log(palindromeFn('aviddiva'))
console.log(palindromeFn('Hello'))

If we run the above code in any browser, it will show the following result.

Output:

"true"
"false"

Palindrome in JavaScript With for Loop

Another method to check if a string is a palindrome or not is by using a for loop. Below are the steps to check if a string is a palindrome in JavaScript.

function palindromeFn(string) {
  const stringLength = string.length;
  for (let i = 0; i < stringLength / 2; i++) {
    if (string[i] !== string[stringLength - 1 - i]) {
      return 'It is not a palindrome.';
    }
  }
  return 'It is a palindrome.';
}
console.log(palindromeFn('aviddiva'));
console.log(palindromeFn('Hello'));

If we run the above code in any browser, it will show the following result.

Output:

"It is a palindrome."
"It is not a palindrome."