const target = { name: 'Maya', age: 25 };
const handler = {
  get(obj, prop) {
    if (prop in obj) {
      return obj[prop];
    }
    return `Property '${prop}' not found`;
  },
  set(obj, prop, value) {
    if (typeof value === 'string') {
      obj[prop] = value.toUpperCase();
    } else {
      obj[prop] = value;
    }
    return true;
  }
};
const proxy = new Proxy(target, handler);
proxy.city = 'tokyo';
console.log(proxy.name);
console.log(proxy.city);
console.log(proxy.country);

const a = [1, 2, 3, 4];
console.log(a + "");

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

const result = numbers
  .map(x => x * 2)
  .filter(x => x > 5)
  .reduce((acc, x) => {
    acc.push(x.toString());
    return acc;
  }, [])
  .map(x => x + '!')
  .join(' | ');

console.log(result);
console.log(typeof result);

var a = 5;
function test() {
  console.log(a);
  var a = 10;
  console.log(a);
}

test();

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

const counter = createCounter();

console.log(counter.increment());
console.log(counter.getCount());
console.log(counter.increment());
console.log(counter.getCount());

console.log(false || 1 + true || 2);

const sym1 = Symbol('test');
const sym2 = Symbol('test');
const obj = {
  [sym1]: 'first',
  [sym2]: 'second',
  regular: 'third'
};

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

console.log(keys.length);
console.log(symbols.length);
console.log(allProps.length);
console.log(sym1 === sym2);

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

with (obj) {
  var sum = a + b;
  var greeting = c + ' world';
}

console.log(sum, greeting);

const values = [null, undefined, '', 0, false, NaN];
const results = [];

for (let val of values) {
  results.push({
    value: val,
    boolean: !!val,
    string: String(val),
    number: Number(val)
  });
}

console.log(results[2].boolean);
console.log(results[3].string);
console.log(results[1].number);

function a() {
   console.log(arguments[0]);
}

a([1]);

const array = Array.from({ length: 5 }, () => Math.random() > 0.5);

console.log(array);

class StateMachine {
  constructor() {
    this.state = 'idle';
    this.transitions = {
      idle: { start: 'running' },
      running: { pause: 'paused', stop: 'stopped' },
      paused: { resume: 'running', stop: 'stopped' },
      stopped: { reset: 'idle' }
    };
  }
  
  transition(action) {
    const next = this.transitions[this.state]?.[action];
    if (next) this.state = next;
    return this.state;
  }
}

const sm = new StateMachine();
console.log(sm.transition('start'));
console.log(sm.transition('invalid'));
console.log(sm.transition('pause'));
console.log(sm.transition('resume'));
console.log(sm.transition('stop'));
console.log(sm.transition('reset'));

function* generator() {
  yield 1;
  yield 2;
  yield 3;
}

const gen = generator();

const { value, done } = gen.return('early');

console.log(value, done);

const user = {
   name: 'John',
   age: 35,
};

for (const value in user) {
   console.log(value);
}

console.log('1');

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

Promise.resolve().then(() => console.log('3'));

setTimeout(() => console.log('4'), 0);

Promise.resolve().then(() => {
  console.log('5');
  return Promise.resolve();
}).then(() => console.log('6'));

console.log('7');

const promise = new Promise((resolve, reject) => {
  setTimeout(() => reject(new Error('Error')), 1000);
});

promise
  .then(result => console.log(result))
  .then(result => console.log(result))
  .catch(error => console.error(error.message))
  .finally(() => console.log('Finally'));

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);