console.log('Start');

setTimeout(() => console.log('Timeout 1'), 0);

setTimeout(() => console.log('Timeout 2'), 0);

console.log('End');

const nums = [1, 2, 3];
const obj = { a: 1, b: 2, c: 3 };

function process(...args) {
  const [first, ...rest] = args;
  const { a, ...others } = obj;
  return { first, rest, a, others };
}

const result = process(...nums);
console.log(result.first);
console.log(result.rest.length);
console.log(result.others.b);
console.log(Object.keys(result.others).join(''));
console.log(result.a === nums[0]);

const array = [1, 2, 3, 4];
const result = array.reduceRight((acc, val) => acc - val);

console.log(result);

let obj = { name: 'Sarah', age: 25 };
let weakMap = new WeakMap();
let map = new Map();

weakMap.set(obj, 'weak reference');
map.set(obj, 'strong reference');

console.log(weakMap.has(obj));
console.log(map.has(obj));

obj = null;

console.log(weakMap.has(null));
console.log(map.has(null));
console.log(map.size);

var b = 10;
if (b % 3 == 0) {
   var i = 10;
}
console.log(i);

const x = [1, 2, 3, 4, 5];
console.log(x.slice(1, 3));

function* fibonacci() {
  let [a, b] = [0, 1];
  while (true) {
    yield a;
    [a, b] = [b, a + b];
  }
}

function* takeWhile(generator, predicate) {
  for (const value of generator) {
    if (!predicate(value)) break;
    yield value;
  }
}

const fib = fibonacci();
const smallFibs = takeWhile(fib, x => x < 20);
console.log([...smallFibs].join(','));

let obj = { a: 1 };
Object.freeze(obj);

console.log(Object.isFrozen(obj));
console.log(obj.a = 2);
console.log(obj.a);

const user = {
  name: 'Sarah',
  age: 25,
  getName() { return this.name; },
  getAge: () => this.age
};

const methods = {
  regular: user.getName,
  arrow: user.getAge
};

console.log(methods.regular());
console.log(methods.arrow());
console.log(user.getName());
console.log(user.getAge());

let obj1 = { name: 'Sarah' };
let obj2 = { name: 'Mike' };
let obj3 = { ref: obj1 };

obj1.circular = obj1;
obj2.partner = obj3;
obj3.partner = obj2;

let weakMap = new WeakMap();
weakMap.set(obj1, 'data1');
weakMap.set(obj2, 'data2');

obj1 = null;
obj2 = null;

console.log(weakMap.has(obj3.ref));
console.log(obj3.partner.name);

var str="My name is John";
var words1=str.split(" ",3);
console.log("words1:",words1);
var words2=str.split(" ",5);
console.log("words2:",words2);

function createCounter() {
  let count = 0;
  return {
    increment: () => ++count,
    decrement: () => --count,
    get: () => count
  };
}

const counter1 = createCounter();
const counter2 = createCounter();
counter1.increment();
counter1.increment();
counter2.increment();
console.log(counter1.get(), counter2.get());
const { increment, get } = counter1;
increment();
console.log(get());

async function foo() {
  console.log('Start');
  await Promise.resolve().then(() => {
    console.log('Inside Promise');
  });
  console.log('End');
}

foo();
console.log('Outside');

console.log('Hi' instanceof String);

const promise1 = Promise.resolve('first');
const promise2 = new Promise(resolve => {
  resolve('second');
});

const promise3 = Promise.resolve().then(() => 'third');

async function test() {
  console.log('start');
  
  const result1 = await promise1;
  console.log(result1);
  
  const result2 = await promise2;
  console.log(result2);
  
  const result3 = await promise3;
  console.log(result3);
  
  console.log('end');
}

test();

const person = {};
person.name.toUpperCase();
console.log(person.name);

const matrix = [
  [2, 4],
  [6, 8],
];

const result = matrix.reduceRight((acc, row) => acc.concat(row.map(num => num * 2)), []);

console.log(result);

const firstArrayData = [ 'JavaScript', 'Universe' ];
const secondArrayData = [ 'JavaScript', 'Universe' ];

console.log(firstArrayData == secondArrayData);
console.log(firstArrayData === secondArrayData);

const sym1 = Symbol("id");
const sym2 = Symbol("id");
console.log(sym1 === sym2);

const original = { a: 1, b: { c: 2 } };
const shallow = { ...original };
const deep = JSON.parse(JSON.stringify(original));

shallow.a = 10;
shallow.b.c = 20;

deep.a = 100;
deep.b.c = 200;

const frozen = Object.freeze({ x: 1, y: { z: 2 } });
frozen.x = 99;
frozen.y.z = 99;

console.log(original.a, original.b.c, frozen.x, frozen.y.z);