const user = {
  details: {
    name: 'Alex',
    contact: null,
    preferences: {
      theme: 'dark'
    }
  },
  getInfo() {
    return this?.details?.contact?.email || 
           this?.details?.preferences?.theme || 
           this?.details?.name || 
           'Unknown';
  }
};

console.log(user.getInfo());