function trickyScope() {
    let x = 10;
    if (true) {
        let x = 20;
        console.log(x); // A
    }
    console.log(x); // B
    {
        let x = 30;
        console.log(x); // C
    }
    console.log(x); // D
}

trickyScope();

const person = {
  name: 'Alice',
  age: 25,
  city: 'Wonderland'
};

const additionalInfo = {
  age: 30,
  occupation: 'Explorer'
};

const combined = {
  ...person,
  ...additionalInfo
};

console.log(combined.age);

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

const result = numbers
  .filter(n => n % 2 === 0)
  .map(n => n * 2)
  .reduce((acc, n) => acc + n, 0);

console.log(result);

const compose = (...fns) => fns.reduce((f, g) => (...args) => f(g(...args)));

const pipe = (...fns) => fns.reduce((f, g) => (...args) => g(f(...args)));

const double  = x => x * 2;
const addTen  = x => x + 10;
const square  = x => x * x;
const negate  = x => -x;

const transform1 = compose(negate, square, addTen, double);
const transform2 = pipe(double, addTen, square, negate);

const val = 3;

console.log(transform1(val), transform2(val));

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

const result = numbers
  .filter(n => n % 2 === 0)
  .map(n => n * 2)
  .reduce((acc, n) => acc + n, 0);

console.log(result);

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

const result = numbers
  .filter(num => num % 2 === 0)
  .map(num => num * num)
  .reduce((acc, num) => acc + num, 0);

console.log(result);

function capIt(str){
  return str.split(/ /)
            .map(s=>s.replace(/^./,x=>x.toUpperCase()))
            .join(" ")
}
console.log( capIt("hello world!"))  
console.log( capIt("my name is John."))

const map = new Map();
const key1 = {};
const key2 = key1;

map.set(key1, "Value for key1");
map.set(key2, "Value for key2");

console.log(map.get(key2));
console.log(map.get(key1));

const map = new Map();
const key1 = {};
const key2 = key1;

map.set(key1, "Value for key1");
map.set(key2, "Value for key2");

console.log(map.get(key2));
console.log(map.get(key1));

function Animal(name) {
  this.name = name;
}

Animal.prototype.speak = function() {
  return `${this.name} makes a noise`;
};

function Dog(name) {
  Animal.call(this, name);
}

Dog.prototype = Object.create(Animal.prototype);
Dog.prototype.constructor = Dog;

Dog.prototype.speak = function() {
  return `${this.name} barks`;
};

const animal = new Animal('Animal');
const dog = new Dog('Rex');

console.log(dog instanceof Animal);