function createUser(
  name,
  role = "viewer",
  permissions = [role],
  metadata = { createdBy: name, level: permissions.length }
) {
  return { name, role, permissions, metadata };
}

const user1 = createUser("Carlos");
const user2 = createUser("Diana", "admin", ["read", "write", "delete"]);
const user3 = createUser("Eve", "editor", undefined, { createdBy: "system", level: 99 });

console.log(user1.role, user1.permissions, user1.metadata.level);
console.log(user2.metadata.createdBy, user2.permissions.length);
console.log(user3.permissions[0], user3.metadata.level);