class Counter {
  constructor(max) {
    this.max = max;
  }
  
  *[Symbol.iterator]() {
    let current = 0;
    while (current < this.max) {
      yield current++;
    }
  }
}

const counter = new Counter(3);
const result = [...counter, ...counter];
console.log(result);

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

const result = numbers
  .map(n => n * 2)
  .filter(n => n > 5)
  .reduce((acc, n, index) => {
    acc.sum += n;
    acc.indices.push(index);
    return acc;
  }, { sum: 0, indices: [] });

console.log(result.sum);
console.log(result.indices);

function processData(data) {
  try {
    if (!data) {
      throw new TypeError('Data is missing');
    }
    
    const result = data.process();
    return result;
  } catch (error) {
    console.log(error instanceof ReferenceError ? 1 :
               error instanceof TypeError ? 2 :
               error instanceof SyntaxError ? 3 : 4);
  }
}

processData(null);

const obj = {
  name: 'Sarah',
  getName() {
    return this.name;
  },
  getNameArrow: () => {
    return this.name;
  }
};

const getName = obj.getName;
const getNameArrow = obj.getNameArrow;

console.log(obj.getName());
console.log(getName());
console.log(getNameArrow());
console.log(obj.getNameArrow());

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);