const original = {
  name: 'Sarah',
  scores: [85, 92, 78],
  details: {
    age: 25,
    city: 'Portland'
  }
};

const copy1 = { ...original };
const copy2 = JSON.parse(JSON.stringify(original));

copy1.name = 'Emma';
copy1.scores.push(95);
copy1.details.age = 30;

console.log(original.name, original.scores.length, original.details.age);

const createLogger = (prefix) => (message) => `${prefix}: ${message}`;
const createCounter = () => {
  let count = 0;
  return () => ++count;
};

const withLogging = (fn) => (...args) => {
  const result = fn(...args);
  console.log(`Called with: ${args}, Result: ${result}`);
  return result;
};

const counter = createCounter();
const loggedCounter = withLogging(counter);
const logger = createLogger('INFO');

console.log(loggedCounter());
console.log(logger(loggedCounter()));

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 = {
  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();

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);