// JavaScript is the language of the web
const greet = (name) => {
  return `Hello, ${name}!`;
};

// Promises & Async/Await
async function fetchData(url) {
  try {
    const res = await fetch(url);
    const data = await res.json();
    return data;
  } catch (err) {
    console.error('Oops:', err);
  }
}

// Closures
function counter() {
  let count = 0;
  return {
    increment: () => ++count,
    decrement: () => --count,
    value: () => count,
  };
}

// Event delegation
document.addEventListener('click', (e) => {
  if (e.target.matches('.btn')) {
    handleClick(e.target);
  }
});

// Debounce
const debounce = (fn, delay) => {
  let timer;
  return (...args) => {
    clearTimeout(timer);
    timer = setTimeout(() => fn(...args), delay);
  };
};

// Prototype chain
class Animal {
  constructor(name) {
    this.name = name;
  }
  speak() {
    return `${this.name} makes a sound.`;
  }
}

class Dog extends Animal {
  speak() {
    return `${this.name} barks.`;
  }
}

// Spread & destructuring
const { a, b, ...rest } = obj;
const merged = { ...defaults, ...overrides };

// Array methods
const doubled = nums
  .filter(n => n > 0)
  .map(n => n * 2)
  .reduce((acc, n) => acc + n, 0);