mutationsa FreeCodeCamp challenge
function mutation(arr) {
  var first = arr[0].toLowerCase();
  var second = arr[1].toLowerCase().split('');
  var wahr = '';
  for (var i = 0; i< second.length; i++) {
    switch (first.indexOf(second[i])) {
      case ( -1):
        wahr = first.indexOf(second[i]);
        break;
    }
  }
  var result = (wahr === -1) ? false : true;
  console.log('RETURN => ', result);
  overlay(JSON.stringify(result));
  return result;
}