js-algorithms/algorithm9.html at master · klink/js-algorithms · GitHub

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<!DOCTYPE html>
<html>
<body>


<script>
    //https://www.freecodecamp.org/learn/javascript-algorithms-and-data-structures/intermediate-algorithm-scripting/missing-letters
    //Find the missing letter in the passed letter range and return it.
    //If all letters are present in the range, return undefined.

function fearNotLetter(str) {

var length = str.length;
var newArr = str.split("");
newArr = newArr.map(a => a.charCodeAt());

for (var i=0; i<(newArr.length)-1; i++) {
    var misChar = newArr[i] + 1;
   if (misChar == newArr[i+1]) {
       continue;
   } else {
       return String.fromCharCode(misChar);
   }
}
return undefined;

}


//tests

console.log(fearNotLetter("abce"));
console.log(fearNotLetter("abcdefghjklmno"));
console.log(fearNotLetter("stvwx"));
console.log(fearNotLetter("abcdefghijklmnopqrstuvwxyz"));


</script>

</body>
</html>