class Vehicle {
  constructor(type) {
    this.type = type;
  }
  describe() {
    return `I am a ${this.type}`;
  }
}

class Car extends Vehicle {
  constructor(brand) {
    super("car");
    this.brand = brand;
  }
  describe() {
    return `${super.describe()} made by ${this.brand}`;
  }
}

const myCar = new Car("Toyota");

console.log(myCar.describe());
console.log(myCar instanceof Car);
console.log(myCar instanceof Vehicle);
console.log(Object.getPrototypeOf(Car) === Vehicle);

const compose = (...fns) => (x) => fns.reduceRight((acc, fn) => fn(acc), x);
const pipe = (...fns) => (x) => fns.reduce((acc, fn) => fn(acc), x);

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 input = 3;

console.log(transform1(input));
console.log(transform2(input));
console.log(transform1(input) === transform2(input));

class Session {
  #id;
  constructor(id) {
    this.#id = id;
  }
  getId() { return this.#id; }
}

const activeSessions = new WeakSet();

const s1 = new Session("user_42");
const s2 = new Session("user_99");
let s3 = new Session("user_07");

activeSessions.add(s1);
activeSessions.add(s2);
activeSessions.add(s3);

console.log(activeSessions.has(s1));         // line A
console.log(activeSessions.has(s3));         // line B

s3 = null;

console.log(activeSessions.has(s3));         // line C

activeSessions.delete(s2);
console.log(activeSessions.has(s2));         // line D
console.log(activeSessions.size);            // line E

const inventory = {
  apples: 5,
  bananas: 0,
  cherries: 12,
  dates: undefined,
  elderberries: null,
};

const summary = Object.entries(inventory)
  .filter(([_, value]) => value)
  .reduce((acc, [key, value]) => {
    acc[key] = value * 2;
    return acc;
  }, {});

console.log(Object.keys(summary).length);
console.log(Object.values(summary).every(v => v > 10));
console.log(Object.keys(inventory).length === Object.keys(summary).length);

const user = {
  profile: {
    getName: () => "Marcus",
    getAge: () => 30,
  },
  settings: null,
};

const name = user.profile?.getName?.();
const age = user.profile?.getAge?.();
const theme = user.settings?.getTheme?.() ?? "dark";
const lang = user.address?.getLocale?.() ?? "en-US";

console.log(`${name} | ${age} | ${theme} | ${lang}`);

let x = 'global';

function testScope() {
  console.log(x);
  
  if (true) {
    let x = 'block';
    var y = 'function';
    console.log(x);
  }
  
  console.log(x);
  console.log(y);
}

testScope();