JSFiddle - React, Tailwind, and code Playground

JavaScript

function isPalindrome(s,i) {
 return(i=i||0)<0||i>=s.length>>1||s[i]==s[s.length-1-i]&&isPalindrome(s,++i);
}

function checkPalindrom(str) {
    return str == str.split('').reverse().join('');
}

var dt = new Date();
var i;
var max = 1000000;
for(i = 0; i < max; i++) {
  isPalindrome('racecar');
}
var isPalindromeTime = Date.now() - dt.getTime();

dt = new Date();
for(i = 0; i < max; i++) {
  checkPalindrom('racecar');
}
var checkPalindromTime = Date.now() - dt.getTime();

var factor;
var message;
if (isPalindromeTime < checkPalindromTime) {
  factor = checkPalindromTime / isPalindromeTime;
  message = 'isPalindrome is faster than checkPalindrom by ~' + factor.toFixed(2) + ' times.';
} else {
  factor = isPalindromeTime / checkPalindromTime;
  message = 'checkPalindrom is faster than isPalindrome by ~' + factor.toFixed(2) + ' times.';
}
console.log(message);