// Check if a string is an isogram
function isIsogram(str){
   return !str.match(/([a-z]).*\1/i);
  //or: return new Set(str.toLowerCase()).size === str.length;
}
console.log(isIsogram("Dermatoglyphics"));//, true
console.log(isIsogram("isogram"));          //, true
console.log(isIsogram("moOse"));          //, false
console.log(isIsogram("isIsogram"));      //, false
console.log(isIsogram(""));                  //, true