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 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);

const data = {
  name: '',
  age: 0,
  city: null,
  country: undefined,
  isActive: false
};

const getName = () => data.name || 'Unknown';
const getAge = () => data.age ?? 25;
const getCity = () => data.city || 'Default City';
const getCountry = () => data.country ?? 'Default Country';
const getStatus = () => data.isActive || 'inactive';

console.log(`${getName()}-${getAge()}-${getCity()}-${getCountry()}-${getStatus()}`);

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);

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);

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'));

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');