function mutation(arr) {
  var arrFirst = arr[0].toLowerCase();
  var arrSecond = arr[1].toLowerCase();
  var tester;
  for(var i = 0; i < arrSecond.length; i++) {
    if (arrFirst.indexOf(arrSecond.charAt(i)) < 0) {
     return false;
    }  
  }
  return true;
 }

mutation(["hello", "hey"]);