javascript - Palindrome Checker does not catch 'almostomla'

Question

I write palindrome checker. It works for all the test case scenarios but "almostomla" and I don't know why.

My code:

function palindrome(str) {
  //deleting all non-alphanumeric characters from the array and changing all the remaining characters to lowercases
  str = str.replace(/[_W]+/g, "").toLowerCase();

  const a = str.split('');
  console.log(a);
  const b = [...a].reverse().join('');
  console.log(b);
  const c = [...a].join('');
  console.log(c);

  for(var i=0; i<b.length; i++){
    if(b[i] !== c[i]){
      return false;
    } else {
      return true;
    }
  }
}

console.log(palindrome("almostomla"));

question from:https://stackoverflow.com/questions/65834320/palindrome-checker-does-not-catch-almostomla

Answer 1

for(var i=0; i<b.length; i++){
  if(b[i] !== c[i]){
    return false;
  } else {
    return true;
  }
}

This for loop here is going to compare the first characters, and then return. It won't look at the second characters. You'll need to set up the loop so it keeps going through the entire word. It can bail out once it knows it's not a palindrome if you like

For example:

for(var i=0; i<b.length; i++){
  if(b[i] !== c[i]){
    return false;
  }
}

return true;

As evolutionxbox mentions, there's also a simpler option: you can compare the entire strings instead of comparing one character at a time. If two strings have identical characters, they will pass a === check:

function palindrome(str) {
  //deleting all non-alphanumeric characters from the array and changing all the remaining characters to lowercases
  str = str.replace(/[_W]+/g, "").toLowerCase();

  const a = str.split('');
  const b = [...a].reverse().join('');
  const c = [...a].join('');

  return b === c;
}

console.log(palindrome("almostomla"));
console.log(palindrome("aha"));