const numbers = [1, 2, 3, 4, 5];

const sum = numbers.reduce((acc, curr) => {
  setTimeout(() => {
    acc += curr;
  }, 0);
  return acc;
}, 0);

console.log(sum);

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

const counter1 = createCounter();
const counter2 = createCounter();
counter1.increment();
counter1.increment();
counter2.increment();
console.log(counter1.getValue() + counter2.getValue());

const original = {
  name: 'Emma',
  skills: ['JavaScript', 'Python'],
  config: { theme: 'dark', notifications: true }
};

const copy1 = { ...original };
const copy2 = JSON.parse(JSON.stringify(original));
const copy3 = Object.assign({}, original);

copy1.name = 'Sarah';
copy1.skills.push('React');
copy1.config.theme = 'light';

console.log(original.name);
console.log(original.skills.length);
console.log(original.config.theme);

const obj = { a: 1, b: 2, c: 3 };
const result = Object.values(obj).reduce((acc, curr) => acc * curr, 1);
console.log(result);

const obj = {
  name: 'Sarah',
  regularMethod: function() {
    return () => {
      console.log(this.name);
    };
  },
  arrowMethod: () => {
    return () => {
      console.log(this.name);
    };
  }
};

const regular = obj.regularMethod();
const arrow = obj.arrowMethod();
regular();
arrow();

class MyClass {
  constructor() {
    this.value = 42;
  }
}

console.log('1');
setTimeout(() => console.log('2'), 0);
Promise.resolve().then(() => console.log('3'));
setTimeout(() => console.log('4'), 0);
console.log('5');
Promise.resolve().then(() => {
  console.log('6');
  return Promise.resolve();
}).then(() => console.log('7'));
queueMicrotask(() => console.log('8'));
console.log('9');

class EventManager {
  constructor() {
    this.listeners = new Map();
  }
  
  addListener(event, callback) {
    if (!this.listeners.has(event)) {
      this.listeners.set(event, new Set());
    }
    this.listeners.get(event).add(callback);
  }
}

const manager = new EventManager();
const obj = { name: 'Component' };
manager.addListener('click', () => console.log(obj.name));
obj = null;
console.log(manager.listeners.get('click').size);

const step1 = multiply(2);
const step2 = step1(3);
const result1 = step2(4);

const result2 = multiply(2)(3)(4);

const partialMultiply = multiply(5);
const result3 = partialMultiply(2)(3);

const doubler = multiply(2)(1);
const result4 = doubler(7);

console.log(result1, result2, result3, result4);

const multiply = (a) => (b) => (c) => a * b * c;

const step1 = multiply(2);
const step2 = step1(3);
const result1 = step2(4);

const result2 = multiply(2)(3)(4);

const partialMultiply = multiply(5);
const result3 = partialMultiply(2)(3);

const doubler = multiply(2)(1);
const result4 = doubler(7);

console.log(result1, result2, result3, result4);

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

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

const obj = {
  value: 011,
  increment() {
    this.value++;
  }
};

const increment = obj.increment;
increment();

console.log(obj.value);

let obj = { a: 1 };
let proto = { b: 2 };

Object.setPrototypeOf(obj, proto);

for (let key in obj) {
  console.log(key);
}

const symbol1 = Symbol('desc1');
const symbol2 = Symbol('desc2');
const myObject = {};
myObject[symbol1] = 'Value1';
myObject[symbol2] = 'Value2';
let output = '';
for (let key in myObject) {
  output += myObject[key] + ' ';
}
output += Object.getOwnPropertySymbols(myObject).length;
console.log(output);

const cache = new Map();

function createHandler(id) {
  const data = { id, value: new Array(1000).fill(id) };
  cache.set(id, data);
  
  return function(action) {
    if (action === 'get') return data;
    if (action === 'clear') cache.delete(id);
  };
}

const handler1 = createHandler('user-1');
const handler2 = createHandler('user-2');

handler1('clear');
console.log(cache.size);
console.log(handler1('get').id);

function createCounter() {
  let count = 0;
  
  const counter = {
    increment() {
      count++;
      return count;
    },
    getCount() {
      return count;
    }
  };
  
  return counter;
}

let c1 = createCounter();
c1.increment();
c1.increment();

let c2 = c1;
c1 = null;

console.log(c2.getCount());

const obj = { a: 1, b: 2, c: 3 };
const result = Object.values(obj).reduce((acc, curr) => acc * curr, 1);
console.log(result);

const nums = [1, 2, 3, 4, 5];
const result = nums
  .filter(n => n > 2)
  .map(n => n * 2)
  .reduce((acc, n) => {
    acc.push(n + 1);
    return acc;
  }, [])
  .slice(1);

console.log(result);
console.log(nums);

function* generator1() {
  yield 1;
  yield 2;
}

function* generator2() {
  yield* generator1();
  yield 3;
}

const gen = generator2();
console.log(gen.next().value);
console.log(gen.next().value);
console.log(gen.next().value);

const sym1 = Symbol('test');
const sym2 = Symbol('test');
const obj = {
  [sym1]: 'value1',
  [sym2]: 'value2',
  regular: 'value3'
};

const sym3 = Symbol.for('global');
const sym4 = Symbol.for('global');

console.log(sym1 === sym2);
console.log(sym3 === sym4);
console.log(Object.keys(obj).length);
console.log(Object.getOwnPropertySymbols(obj).length);

const regex = /\d{2,}/;
console.log(regex.test('5'), regex.test('55'), regex.test('555'));