Palindrome Test Performance

function isPalindrome (str) {
  return str.toLowerCase().replace(/[\W_]/g, "") ===
  str.toLowerCase().replace(/[\W_]/g, "").split("").reverse().join("");
}

function isPalindrome (str) {
  var sanitizedString = str.toLowerCase().replace(/[\W_]/g, "");
  return sanitizedString === sanitizedString.split("").reverse().join("");
}

function isPalindrome (str) {
  return str.toLowerCase().match(/[a-z]/g).every(function (value, i, str) {
    return value === str[str.length - i - 1];
  });
}

function isPalindrome (str) {
 
 str = str.match(/[a-z]/gi).join('');
 var emptyArray = [];
  
 str.toLowerCase().split('').reduce(function(accumulator, value){
    return emptyArray.unshift(value);
  }, []);
  
    return str.toLowerCase() === emptyArray.join('') ? true:false;
};

function isPalindrome (str) {
  return str.replace(/_ ]/g,"").toLowerCase() == str.replace(/_ ]/g,"").toLowerCase().split('').reverse().join('');
}

function isPalindrome (str) {

var remove = str.toLowerCase().replace(/[^a-z0-9]/g,"");

var reverse = remove.split("").reverse().join("");

return reverse === remove;

};

function isPalindrome (str) {
  str = str.toLowerCase().replace(/[^a-z]/gi, '');
  var letters = str.split('');
  for(var i = 0; i < letters.length/2; i++) {
    if(letters[i] !== letters[letters.length-1-i]){
      return false;
    }
  }
  return true;
};

function isPalindrome (str) {
  // Write your code here, and
  // return your final answer.
  
  // change str to all lowercase and remove any whitespace to easily compare
  str = str.toLowerCase().replace(/\s/g, '');
  
  // reversed str: split str into array, reverse and join back into a string
  strReversed = str.split('').reverse().join('');
  
  // compare both strings
  return strReversed === str;
  
}

function isPalindrome (str) {
  // Write your code here, and
  // return your final answer.
  
  str = str.toLowerCase();
  str = str.replace(/[^a-z]/g,'');
  var strA = str.slice(0,str.length / 2);
  var strB = str.slice(Math.ceil(str.length / 2)).split('').reverse().join('');
  
  console.log(strA  , strB);
  
  return strA === strB;
}

function isPalindrome (str) {
  str = str.toLowerCase().split("");
  str = str.filter(function(space){
    return /\S/.test(space)
  });
  var output = "";
  for(var i = str.length-1; i>=0; i--){
    output += str[i];
  }
  if(output === str.join("")){
    return true;
  }
  return false;
}

function isPalindrome (str) {
  str = str.toLowerCase().replace(/[^a-z]/gi, '');
  if (str.length <= 1) {
    return true;
  }
  if (str[0] !== str[str.length-1]) {
    return false;
  }
  return isPalindrome(str.slice(1, str.length-1));
}

function isPalindrome (str) {
  var str = str.replace(/\s/g,'').toLowerCase().split("");
  var rev = [];
  for (var i = 0; i < str.length; i++) {
    rev[i] = str[str.length-1-i];
  }
  return str.join("") === rev.join("");
}

function isPalindrome (str) {
  var stringy = str.replace(/[^a-z]/gi,'').toLowerCase();
  return stringy.split('').reverse().join('') === stringy;
}

function isPalindrome(str) {
  stringy = str.replace(/[^a-z]/gi,'').toLowerCase();
  var innerFunc = function(strng) {
    if (strng.length <= 1) {
      return true;
    } 
    if (strng[0] !== strng[strng.length - 1]) {
      return false;
    } else {
      return isPalindrome(strng.slice(1, strng.length - 1));
    }
  };
  return innerFunc(stringy);
}

function isPalindrome (str) {
  var i = 0;
  str = str.toLowerCase().split('').reduce(function(onlyLetters, char) {
    if (char.charCodeAt(0) >= 97 && char.charCodeAt(0) <= 122) {
      return onlyLetters + char;
    }
    return onlyLetters;
  }, '');
  
  return str.split('').reverse().reduce(function(isPally, letter) {
    if (letter !== str[i++]) return false;
    return isPally;
  }, true)
}