let a = 'a';
let b = 'c';

(function () {
   console.log(a);
   var a = 'd';
   var b = 'e';
   console.log(b);
})();

console.log(a);
console.log(b);

async function test() {
  console.log('1');
  
  setTimeout(() => {
    console.log('2');
  }, 0);
  
  await Promise.resolve();
  console.log('3');
  
  new Promise(resolve => {
    console.log('4');
    resolve();
  }).then(() => {
    console.log('5');
  });
  
  console.log('6');
}

test();
console.log('7');

function getArr() {
  return Array.from(arguments);
}

var data = [4, 5, 6];

const result = getArr(...[1, 2, 3], ...data);

console.log(result);

function getCity(person) {
  return person?.address?.city ?? 'Unknown';
}

const data = [
  null,
  { name: 'Alice' },
  { name: 'Bob', address: null },
  { name: 'Charlie', address: { street: '123 Main' } },
  { name: 'David', address: { city: 'Boston' } }
];

const cities = data.map(getCity);
console.log(cities);

const weakMap = new WeakMap();
const array = [{}, {}, {}, [], {"s": 1}];

array.forEach(obj => weakMap.set(obj, obj));
const result = array.map(obj => weakMap.get(obj) == obj);

console.log(result);

const array = [1, 2, 3, [4, [5, [6]]]];
const result = array.flat(3).map(n => n * 3);

console.log(result);

const p1 = Promise.resolve(1);
const p2 = new Promise(resolve => resolve(2));
const p3 = new Promise(resolve => setTimeout(() => resolve(3), 0));
const p4 = Promise.reject(4).catch(err => err);

Promise.all([p1, p2, p3, p4])
  .then(values => {
    const result = values.reduce((acc, val) => {
      return acc + val;
    }, 0);
    console.log(result);
  })
  .catch(err => console.log('Error:', err));

function delayedLog(item) {
  setTimeout(() => {
    console.log(item);
  }, 1000);
}
for (var i = 0; i < 3; i++) {
  delayedLog(i);
}

console.log(typeof null);
console.log(typeof function () {});
console.log(typeof {});
console.log(typeof 1);
console.log(typeof '');
console.log(typeof true);
console.log(typeof '{}');

const obj = {
  [Symbol('a')]: 'hidden',
  [Symbol.for('b')]: 'registered',
  c: 'normal'
};

const symbols = Object.getOwnPropertySymbols(obj);
const keys = Object.keys(obj);
const allProps = Reflect.ownKeys(obj);

console.log(symbols.length, keys.length, allProps.length);

function* generator() {
  yield 1;
  yield* [2, 3];
  yield* '4';
}

const gen = generator();
for (const value of gen) {
  console.log(value);
}

function createCounter() {
  let count = 0;
  
  return function() {
    count++;
    return count;
  };
}

const counter1 = createCounter();
const counter2 = createCounter();

counter1();
counter1();
counter2();

const result = counter1() + counter2();
console.log(result);

const weakMap = new WeakMap();
const obj = {};
const gen = (function* () {
  yield 'value1';
  yield 'value2';
  yield* ['value1', 'value2']
})();

weakMap.set(obj, gen.next().value);

console.log(weakMap.get(obj));
console.log(gen.next().value);
console.log(gen.next().value);

const counter = (() => {
  let count = 0;
  
  return {
    increment() {
      count += 1;
      return this;
    },
    reset() {
      count = 0;
      return this;
    },
    get value() {
      return count;
    }
  };
})();

const { increment, value } = counter;

increment();
counter.increment();

console.log(value);

for (var i = 0; i < 3; i++) {
  const log = () => {
    console.log(i)
  }
  setTimeout(log, 1)
}

function recursiveBinarySearch(arr, target, start = 0, end = arr.length - 1) {
  if (start > end) {
    return -1;
  }

  const mid = Math.floor((start + end) / 2);

  if (arr[mid] === target) {
    return mid;
  } else if (arr[mid] < target) {
    return recursiveBinarySearch(arr, target, mid + 1, end);
  } else {
    return recursiveBinarySearch(arr, target, start, mid - 1);
  }
}

const result = recursiveBinarySearch([[[1, 2, 3, 4, 5, [6, 7], 8], 9], 6]);

console.log(result);

function processConfig(config) {
  const defaultPort = 8080;
  const defaultTimeout = 5000;
  
  const port = config?.port ?? defaultPort;
  const timeout = config?.timeout ?? defaultTimeout;
  const debug = config?.debug ?? false;
  
  return { 
    summary: `Port: ${port}, Timeout: ${timeout}, Debug: ${debug ? 'enabled' : 'disabled'}`,
    isUsingDefaults: port === defaultPort && timeout === defaultTimeout
  };
}

const result = processConfig({ port: 0, timeout: null });
console.log(result.summary);

function Car(make) {
  this.make = make;
}

function Truck(make) {
  this.make = make;
}

const car = new Car('Toyota');
const truck = new Truck('Toyota');
var newCar = car;

console.log(car.__proto__ === truck.__proto__);
console.log(car.constructor === truck.constructor);
console.log(car instanceof Truck);
console.log(truck instanceof Car);
console.log(Truck.prototype.isPrototypeOf(car));
console.log(Car.prototype.isPrototypeOf(truck));
console.log(truck === car);
console.log(newCar === car);

function processUserData(data) {
  const settings = {
    theme: data.preferences?.theme ?? 'light',
    notifications: data.preferences?.notifications ?? true,
    fontSize: data.preferences?.fontSize ?? 16
  };
  
  let status = data.status ?? 'active';
  let reputation = data.reputation ?? 0;
  
  console.log(reputation || 'No reputation yet');
  return settings;
}

processUserData({ status: '', reputation: 0 });

const value = { number: 100 };
function increment(obj) {
  obj.number++;
}
increment(value);
console.log(value.number);