closure, callback

// Prototypal Inheritance 
function Animal(name) { 
this.name = name; 
} 
Animal.prototype.speak = function() { 
console.log(`${this.name} makes a noise.`); 
}; 
function Dog(name) { 
Animal.call(this, name); // Call the parent constructor 
} 
Dog.prototype = Object.create(Animal.prototype); 
Dog.prototype.constructor = Dog; 
Dog.prototype.speak = function() { 
console.log(`${this.name} barks.`); 
}; 
// Closure 
function createCounter() { 
let count = 0; // Private variable 
return { 
increment: function() { 
count++; 
return count; 
}, 
decrement: function() { 
count--; 
return count; 
}, 
getCount: function() { 
return count; 
} 
}; 
} 
// Callback 
function fetchData(callback) { 
setTimeout(() => { 
const data = { message: "Data fetched!" }; 
callback(data); 
}, 1000); 
} 
// Promise 
function fetchDataPromise() { 
return new Promise((resolve, reject) => { 
setTimeout(() => { 
const data = { message: "Data fetched with Promise!" }; 
resolve(data); 
}, 1000); 
}); 
} 
// Async/Await 
async function fetchDataAsync() { 
const data = await fetchDataPromise(); 
console.log(data.message); 
} 
// Demonstration 
function demo() { 
// Prototypal Inheritance 
const dog = new Dog('Buddy'); 
dog.speak(); // Output: Buddy barks. 
// Closure 
const counter = createCounter(); 
console.log(counter.increment()); // Output: 1 
console.log(counter.increment()); // Output: 2 
console.log(counter.decrement()); // Output: 1 
console.log(counter.getCount()); // Output: 1 
// Callback 
fetchData((data) => { 
console.log(data.message); // Output: Data fetched! 
}); 
// Promise 
fetchDataPromise().then((data) => { 
console.log(data.message); // Output: Data fetched with Promise! 
}); 
// Async/Await 
fetchDataAsync(); // Output: Data fetched with Promise! 
} 
// Run the demonstration 
demo();