IsPalindrome.js

/**
 * @function isPalindromeIterative
 * @description isPalindromeIterative function checks whether the provided input is palindrome or not
 * @param {String | Number} x - The input to check
 * @return {boolean} - Input is palindrome or not
 * @see [Palindrome](https://en.wikipedia.org/wiki/Palindrome)
 */

/*
 * Big-O Analysis
 * Time Complexity
 - O(N) on average and worst case scenario as input is traversed in linear fashion
 - O(1) on best case scenario if the input already is a string (otherwise toString() method takes O(N))
 and the first & last characters don't match, triggering an early return
 * Space Complexity
 - O(1)
*/

export function isPalindromeIterative(x) {
 if (typeof x !== 'string' && typeof x !== 'number') {
 throw new TypeError('Input must be a string or a number')
 }

 // Convert x to string whether it's number or string
 const string = x.toString()
 const length = string.length

 if (length === 1) return true

 // Apply two pointers technique to compare first and last elements on each iteration
 for (let start = 0, end = length - 1; start < end; start++, end--) {
 // Early return if compared items are different, input is not a palindrome
 if (string[start] !== string[end]) return false
 }
 // If early return in condition inside for loop is not reached, then input is palindrome
 return true
}