var wrapperEle = document.body.querySelector(".wrapper");

var alphabet = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"];

var name = prompt("Hello, what is your name? ")

function nameSplit (firstLetter) {
  var nameMod = name.toLowerCase();
  var firstLetter = nameMod.charAt(0);
  return firstLetter;
}

function lookArray () {
  var length = alphabet.length;
  for (var i = 0; i < length ; i++)  {
    if (alphabet[i] = nameSplit(name)) {
      var index = alphabet.indexOf(nameSplit(name));
      wrapperEle.innerHTML = index;
   }
  }
}

lookArray();