Missing letters.md

Find the missing letter in the passed letter range and return it.

If all letters are present in the range, return undefined.

String Global Object String fromCharCode() Method

function fearNotLetter(str) {
  for (let i = 0; i < str.length; i++) {
    let asciiCode = str.charCodeAt(i);
  if (asciiCode !== str.charCodeAt(0) + i) {
    return String.fromCharCode(asciiCode - 1)
    }
  }
  return undefined;
}

fearNotLetter("abce");

• Using Reduce

function fearNotLetter(str) {
  var lost;
  str = str.split('');
  str.reduce(function(acc, val){
    if (val.charCodeAt() - acc.charCodeAt() != 1) 
      lost = String.fromCharCode(val.charCodeAt() - 1);
    return val;
  }, String.fromCharCode(str[0].charCodeAt() - 1));
  return lost;
}

fearNotLetter("de");