Null Object Pattern

Defensive null checks scattered throughout code are a smell.

// dirty — null checks everywhere
interface User { name: string; email: string; role: string; }

function solve(user: User | null | undefined) {
  const name = user ? user.name : 'Anonymous';
  const email = user ? user.email : 'no-email@placeholder.com';
  const role = user ? user.role : 'guest';
  return { name, email, role };
}

Refactor using a Null Object: create a GUEST_USER constant that provides safe defaults, then use it when user is falsy.

solve(null) → { name: 'Anonymous', email: 'no-email@placeholder.com', role: 'guest' }