const user = {
  profile: {
    settings: {
      theme: 'dark',
      notifications: null
    }
  }
};

const getNotificationSound = (user) => {
  return user?.profile?.settings?.notifications?.sound ?? 'default';
};

console.log(getNotificationSound(user));
console.log(getNotificationSound(null));
console.log(getNotificationSound({ profile: {} }));

function processData() {
  try {
    console.log('start');
    throw new Error('oops');
    console.log('unreachable');
  } catch (e) {
    console.log('caught');
    return 'error';
  } finally {
    console.log('cleanup');
  }
  console.log('end');
}

const result = processData();
console.log(result);

const target = { name: 'Sarah', age: 25 };

const handler = {
  get(obj, prop) {
    if (prop === 'toString') {
      return () => `Person: ${obj.name}`;
    }
    return Reflect.get(obj, prop);
  },
  set(obj, prop, value) {
    if (prop === 'age' && value < 0) {
      return false;
    }
    return Reflect.set(obj, prop, value);
  }
};

const proxy = new Proxy(target, handler);
proxy.age = -5;
proxy.location = 'NYC';
console.log(proxy.toString());
console.log(proxy.age);
console.log(proxy.location);

const obj = {
  name: 'Sarah',
  greet() {
    console.log(`Hello, ${this.name}`);
  }
};

const person = { name: 'Mike' };
const func = obj.greet;

obj.greet();
func();
func.call(person);
person.hello = obj.greet;
person.hello();

const source = { a: 1, b: { c: 2 } };
const target1 = Object.assign({}, source);
const target2 = { ...source };

source.b.c = 99;
target1.a = 10;
target2.b.c = 50;

console.log(source.a);
console.log(source.b.c);
console.log(target1.a);
console.log(target1.b.c);
console.log(target2.a);
console.log(target2.b.c);

const memoize = (fn) => {
  const cache = new Map();
  return (...args) => {
    const key = JSON.stringify(args);
    if (cache.has(key)) return cache.get(key);
    const result = fn(...args);
    cache.set(key, result);
    return result;
  };
};

const fibonacci = memoize((n) => {
  if (n <= 1) return n;
  return fibonacci(n - 1) + fibonacci(n - 2);
});

console.log(fibonacci(10));
console.log(fibonacci(5));
console.log(fibonacci(10));

let counter = 0;

const increment = () => ++counter;
const getValue = () => counter;

const obj = {
  get value() { 
    increment();
    return getValue();
  }
};

console.log(obj.value);
console.log(obj.value);
console.log(counter);

const target = { name: "Sarah", age: 25 };

const handler = {
  get(obj, prop) {
    if (prop === 'greeting') {
      return `Hello, I'm ${obj.name}`;
    }
    return obj[prop]?.toString().toUpperCase() || 'UNKNOWN';
  },
  
  set(obj, prop, value) {
    if (typeof value === 'string') {
      obj[prop] = value.toLowerCase();
    } else {
      obj[prop] = value * 2;
    }
    return true;
  }
};

const proxy = new Proxy(target, handler);
console.log(proxy.name);
proxy.city = "Boston";
proxy.score = 15;
console.log(proxy.greeting);
console.log(proxy.city + " " + proxy.score);