Check if a string is a palindrome or not? - Efficient Method

palindrome1

//using normal reversing techinque
function palindrome1(str){
  //removing space and non-alphanumeric characters;
  str = str.toLowerCase().replace(/[^0-9|a-z]/g,'');
  //reversing the string
    var str2 = str.toLowerCase().replace(/[^0-9|a-z]/g,'').split('').reverse().join(''); 
  //checking if both are equal
  if(str === str2)
       return true;
    else
      return false;
}

console.log(palindrome1("e  ye"));

//using half then number of characters for comparison
function palindrome2(str){
  //removing space, non-alphanumeric characters
  str = str.toLowerCase().replace(/[^0-9|a-z]/g,'');
  //
  for(var i=0; i<str.length/2; i++){
    if(str[i] !== str[str.length - i -1]){
      return false;
    }
  }
  return true;
}

console.log(palindrome2("e ye"));