Documentation Arrays Strings

Module

strings

Collection of array manipulation algorithms including searching, sorting, and sum-based problems.

View Source strings/index.js, line 1

Methods

# static isPalindrome(str) → {boolean}

Checks if a given string is a palindrome (reads the same forwards and backwards).

This implementation normalizes the input by converting to lowercase and removing non-alphanumeric characters before comparison. It uses two pointers approach for efficient checking.

Algorithm

  • Clean the input string by removing non-alphanumeric characters and converting to lowercase.
  • Use two pointers (start and end) to compare characters from both ends moving inward.
  • If any mismatch is found, return false.
  • If all characters match, return true.

Constraints

  • Input string can contain letters, numbers, spaces, and special characters.
  • Comparison is case-insensitive.
  • Non-alphanumeric characters are ignored.
  • Empty strings and single characters are considered palindromes.

Edge Cases

  • Empty string returns true.
  • Single character returns true.
  • Strings with only spaces/special characters return true.
  • Handles Unicode characters.
Complexity:
  • Time: O(n) — Where n is the length of the cleaned string.
  • Space: O(n) — For storing the cleaned string.
Parameters:
Name Type Description
str string

The string to check for palindrome property.
Since:
  • 1.0.0
Author:
  • Shonjoy
See:
  • isAnagram - For checking if two strings are anagrams
  • reverseString - For reversing a string
  • Palindrome (Wikipedia)

View Source strings/isPalindrome.js, line 2

If input is not a string.

TypeError

Returns true if the string is a palindrome, false otherwise.

boolean
Examples

Basic palindrome check

isPalindrome("racecar");
// → true

Case-insensitive check

isPalindrome("RaceCar");
// → true

Ignores spaces and punctuation

isPalindrome("A man, a plan, a canal: Panama");
// → true

Non-palindrome string

isPalindrome("hello");
// → false

Empty string is palindrome

isPalindrome("");
// → true

Single character is palindrome

isPalindrome("a");
// → true

Numbers in string

isPalindrome("12321");
// → true

Real-world usage: Form validation

const userInput = "Was it a car or a cat I saw?";
if (isPalindrome(userInput)) {
  console.log("That's a palindrome!");
}