palindrome-for-your-dome.md

Description

A palindrome is a word, phrase, number, or other sequence of symbols or elements, whose meaning may be interpreted the same way in either forward or reverse direction. Famous examples include "Amore, Roma", "A man, a plan, a canal: Panama" and "No 'x' in 'Nixon'". - wikipedia

Our goal is to determine whether or not a given string is a valid palindrome or not.

Like the above examples, here are a few test cases which are also populated:

"Amore, Roma" => valid
"A man, a plan, a canal: Panama" => valid
"No 'x' in 'Nixon'" => valid
"Abba Zabba, you're my only friend" => invalid

You can see that they are case insensitive and disregards non alphanumeric characters. In addition to a few predefined tests, your function will also be tested against a random string generator 50 times which are guaranteed to produce valid palindromes.

NOTE: reverse/reverse! have been disabled for String/Array and reverse() for JS.

Kata's link: Palindrome for your Dome

Best Practices

First:

function palindrome(string) {
  var sanitized = string.replace(/[^A-Za-z]/g, "").toLowerCase();
  return sanitized == sanitized.split("").reduceRight(function(sum, v) {return sum + v;});
}

Second:

function palindrome(string) {
  var s = string.replace(/[^A-Za-z0-9]/g, "").toLowerCase();
  for (var i = 0; i < s.length/2; i++) if (s[i] != s[s.length-i-1]) return false;
  return true;
}

Third:

function palindrome(string) {
  var s = string.toLowerCase().replace(/[^a-z0-9]+/g, '');
  return s == s.split('').reduce(function(str, value) {
    return value+str;
  }, '');
}

Fourth:

function palindrome(string) {
  return string.toLowerCase().replace(/[^a-z]/gi,'').split('').every(function(a,b,c){
    return a===c[c.length-b-1]
  })
}

Fifth:

function palindrome(string) {
  return string
    .toLowerCase()
    .replace(/[^a-z]/g,'')
    .split("")
    .every(function(v, i, array){ return v == array[array.length-i-1] })
  ;
}

My solutions

function palindrome(string) {
  // enter the codes
  let strArr = string.toLowerCase().split('');
  let newArr = string.toLowerCase().split('');
  
  strArr.reverse();
  
  let isPalindrome = false;
  
  strArr = strArr.filter(function(item){
    return /[a-z]/.test(item);
  });
  
  newArr = newArr.filter(function(item){
    return /[a-z]/.test(item);
  });
  
  let len = strArr.length;
  let end = len - 1;
  
  for(let i=0; i < len; i++){
    if(strArr[i] == newArr[end - i]){
      isPalindrome = true;
    } else {
      isPalindrome = false;
      break;
    }
  }
  
  return isPalindrome;
}