To return true or false if a statement is palindrome, i.e same when spelt backward

isPalindrome.js

function isPalindrome(str) {
  // convert string to lowercase
  str = str.toLowerCase();
  // convert string to an array
  let strArr = str.split('');
  // what it will be checked against to eliminitate non alphabetic characters
  let AlphabetArr = 'abcdefghijklmnopqrstuvwxyz'.split('');
  
  // initialize an empty array
  let newContainer = []
  strArr.forEach(char => {
    if(AlphabetArr.indexOf(char) > -1) {
      newContainer.push(char) 
    }
  })
    if(newContainer.join('') === newContainer.reverse().join('')) {
      return true;
    }
    return false;
}