async function asyncChain() {
   const values = [2, 3, 5, 7, 0];
   const total = await values.reduce(async (acc, values) => {
      const current = await acc;
      return current * values;
   }, Promise.resolve(1));
   return total;
}

asyncChain().then(result => console.log(result));

var obj = { a: 10, b: 20 };

with (obj) {
  let result = a + b;
}

console.log(result);

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

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

function multiply(a, b) {
  if (b === 0) {
    return 0;
  } else if (b > 0) {
    return a + multiply(a, b - 1);
  } else {
    return -multiply(a, -b);
  }
}

console.log(multiply(-7, -5));

function processData({ a = 10, b = 20 } = { a: 30 }) {
  console.log(a, b);
}

processData({ a: 5, b: 10 });
processData();

const config = {
  port: 0,
  timeout: null,
  retries: '',
  cache: false,
  debug: undefined
};

const port = config.port ?? 3000;
const timeout = config.timeout ?? 5000;
const retries = config.retries ?? 3;
const cache = config.cache ?? true;
const debug = config.debug ?? false;

console.log([port, timeout, retries, cache, debug]);

const regex = /^pear/gm;
const str = `dog
cat
bat`;
console.log(str.match(regex));

function* gen() {
  yield* ['x', 2, 3].map(x => x * 2);
}

const iterator = gen();
console.log(iterator.next().value);
console.log(iterator.next().value);
console.log(iterator.next().value);
console.log(iterator.next().value);

function test() {
  console.log(arguments.length);
}

test(1, 2, 3);
test.call(null, null, null, null);

const team = {
  captain: { name: 'Jack', age: 35 },
  players: ['Bob', 'Alice', 'Mike'],
  details: { founded: 2020, league: 'Premier' }
};

const { 
  captain: { name }, 
  players: [, second],
  details: { league: division = 'Amateur' } 
} = team;

console.log(`${name}-${second}-${division}`);

const handler = {
  get: (target, prop) => {
    if (prop in target) {
      return target[prop] * 2;
    }
    return 100;
  }
};

const nums = new Proxy({ a: 5, b: 10 }, handler);
console.log(nums.a, nums.b, nums.c);

async function fetchData() {
  const promise = new Promise(resolve => {
    setTimeout(() => resolve('first'), 2000);
  });
  
  console.log('start');
  const result = await promise;
  console.log(result);
  console.log('end');
}

fetchData();
const x = 'after';
console.log(x);

const map = new Map();
const key1 = {};
const key2 = key1;

map.set(key1, "Value for key1");
map.set(key2, "Value for key2");

console.log(map.get(key2));
console.log(map.get(key1));

function* counter() {
  let count = 1;
  while (true) {
    const reset = yield count;
    count = reset ? 1 : count + 1;
  }
}

const gen = counter();
console.log(gen.next().value);
console.log(gen.next().value);
console.log(gen.next(true).value);
console.log(gen.next().value);

function foo() {
    var secondDigit = 1
    let firstDigit = secondDigit
    firstDigit++
    return firstDigit
}
 
foo()
console.log(typeof firstDigit)
console.log(typeof secondDigit)

var a=[1,3,6,9,12,24,36,72,15]
var b=a.filter(x=>x%2==0&&x%3==0&&x%4==0)
console.log(b)

const user = {
  profile: {
    name: "Alice",
    settings: null
  },
  getPreferences() {
    return this.profile.settings?.theme || "default";
  }
};

const admin = {
  profile: {
    name: "Admin"
  },
  getPreferences() {
    return this.profile.settings?.theme || "default";
  }
};

console.log(user.getPreferences());
console.log(admin.getPreferences());
console.log(user.profile.extra?.id?.toString());

const arr = [3, 8, 12];
const even = (elem) => elem % 2 === 0;

console.log(arr.map(even));