Palindromes in JavaScript

palindrome.js

const word = "A man, a plan, a canal. Panama";

/*
 * Checks if a string is a palindrome (as explained here: https://medium.freecodecamp.org/two-ways-to-check-for-palindromes-in-javascript-64fea8191fd7
 * hard polindrome will not except string with white space. 
*/
const palindrome = (w, hard = false) => {
  const str = hard ? w : w.toLowerCase().replace(/[^a-zA-Z0-9]/g,"");
  const left = str.substring(0, Math.floor(str.length/2));
  const right = str.substring(Math.ceil(str.length/2)).split("").reverse().join("");
  return left === right;
};

console.log(palindrome(word));