var UserName = prompt("Who's there?");
if (UserName == "Cancel" || UserName === "") {
  alert("Canceled");
} else if (UserName == "Admin") {
  var Admin = prompt("Password?");
  Admin == "Cancel"
    ? alert("Canceled")
    : Admin == "TheMaster"
    ? alert("Welcome!")
    : alert("Wrong Password!");
} else {
  alert("I don't know you!");
}