Question 202544 in Javascript Question posted in
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JavaScript palindrome checker. What is wrong with this code? The input "almostoma" should have given a false output, but my code gives a true output

It works just fine with other palindromes (e.g "Able was I saw Elba.", "A man, a plan, a canal. Panama."), but fails with "almostoma".

function palindrome(str) {
  str = str.toLowerCase();
  str = str.split(" ").join("");
  str = str.replace(",", "");
  str = str.replace("_", "");
  str = str.replace(".", "");
  for (var i = 0; i < str.length; i++) {
    if (str[i] == str[str.length - i - 1]) {
      return true;
    } else {
      return false;
    }
  }
}
console.log(palindrome("almostoma"));
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2

Answers


  1. 0

    What your code does is that as soon as the if (str[i] == str[str.length - i - 1]) is true, the program returns and it stops executing. Meaning only the last character is checked for equality

    What I advise is to check for inequality only:

    function palindrome(str) {
  str = str.toLowerCase();
  str = str.split(" ").join("");
  str = str.replace(",", "");
  str = str.replace("_", "");
  str = str.replace(".", "");
  for (var i = 0; i < str.length; i++) {
    if (str[i] != str[str.length - i - 1]) {
      return false;
    }
  }
  return true;
}
console.log(palindrome("almostoma"));
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  2. 0

    See the other answers and comment for the error you made

    Here is a different approach

    const palindrome = (str) => {
  str = String(str).toLowerCase(); // handle numbers too
  str = str.replace(/[^p{L}p{N}]/gu, ''); // remove all non characters unicode aware
  return str === [...str].reverse().join(''); // compare the reversed string
}

console.log(palindrome("almostoma"));
console.log(palindrome("Able was I saw Elba."))
console.log(palindrome("A man, a plan, a canal. Panama."))
console.log(palindrome(88000088))
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