Missing letters failing despite console showing otherwise

Tell us what’s happening:
So the challenge requires a missing letter of an alphabetic sequence to be returned. I’ve tested my solution with all the test input strings, and just before I return the result, I log it to the console, which always shows the correct letter. The line near the end where I enclose it in typical string brackets ("") doesn’t change the console result, nor the returned result, as displayed by all the challenges failing. I know it doesn’t return undefined, and the Get A Hint tab suggests using charCodeAt() somewhere, which I could do, but as of now I am more curious as to why the challenges fail, which according to the console, they do not.

Thank you in advance for any help!
Marcus.

Your code so far


function fearNotLetter(str) {
  let newStr = str;
  newStr = newStr.split("");
  console.log(newStr);
  let alpbet = "abcdefghijklmnopqrstuvwxyz";
  alpbet = alpbet.split("");
  console.log(alpbet);

  let indexStart = alpbet.indexOf(newStr[0]);
  let indexEnd = alpbet.indexOf(newStr[newStr.length-1]);

  console.log(indexStart);
  console.log(indexEnd);
  let comparator = alpbet.slice(indexStart,indexEnd+1);
  console.log(comparator);

  let result = comparator.filter( letter => {
    if (newStr.indexOf(letter)!=-1) {
      return false;
    } else {
      return true;
    }
  })
  
  console.log(result);
  result = `"${result}"`; //Challenges still fail if omitted
  console.log(result);

  return result;
}

fearNotLetter("abcdefghjklmno");

Your browser information:

User Agent is: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/69.0.3497.100 Safari/537.36.

Link to the challenge:
https://learn.freecodecamp.org/javascript-algorithms-and-data-structures/intermediate-algorithm-scripting/missing-letters

Although I thought I had evaded this problem, your comment made me think it through, and by removing the double quotes the problem was solved. Thank you for the advice, Randell!