const curry = (fn) => {
  return function curried(...args) {
    if (args.length >= fn.length) {
      return fn.apply(this, args);
    }
    return (...nextArgs) => curried(...args, ...nextArgs);
  };
};

const multiply = (a, b, c) => a * b * c;
const curriedMultiply = curry(multiply);

const step1 = curriedMultiply(2);
const step2 = step1(3);
const result = step2(4);

console.log(result);

const a = { x: 1 };
const b = a;
const c = { x: 1 };

b.x = 2;
const d = b;
d.x = 3;

console.log(a.x);
console.log(b.x);
console.log(c.x);
console.log(a === b);
console.log(a === c);

class Subject {
  constructor() {
    this.observers = [];
  }
  attach(observer) {
    this.observers.push(observer);
  }
  notify(data) {
    this.observers.forEach(obs => obs.update(data));
  }
}

const subject = new Subject();
subject.attach({ update: (d) => console.log(d * 2) });
subject.attach({ update: (d) => console.log(d + 5) });
subject.notify(10);

const obj = { a: 1, b: 2, c: 3 };
Object.defineProperty(obj, 'd', { 
  value: 4, 
  enumerable: false 
});

const entries = Object.entries(obj);
const keys = Object.keys(obj);
const values = Object.values(obj);

console.log(entries.length + keys.length + values.length);

function Vehicle(type) {
  this.type = type;
}

Vehicle.prototype.wheels = 4;
Vehicle.prototype.getInfo = function() {
  return `${this.type}: ${this.wheels}`;
};

const car = new Vehicle('Car');
const bike = Object.create(car);
bike.type = 'Bike';
bike.wheels = 2;

console.log(car.getInfo() + ' | ' + bike.getInfo());

const x = null;
const y = undefined;
const z = 0;

const result1 = x ?? 'default';
const result2 = y ?? 'default';
const result3 = z ?? 'default';

const combined = result1 ? result2 ? result3 : 'B' : 'C';

console.log(combined);

function Vehicle(type) {
  this.type = type;
  this.wheels = 4;
}

Vehicle.prototype.describe = function() {
  return `${this.type} with ${this.wheels} wheels`;
};

const car = new Vehicle('Car');
const bike = Vehicle('Bike');

console.log(car.describe());
console.log(typeof bike);
console.log(globalThis.type);

const json = '{"name":"Sarah","age":25,"active":true}';
const obj = JSON.parse(json);

obj.name = "Emma";
obj.age++;

const json2 = JSON.stringify(obj);
const obj2 = JSON.parse(json2);

obj.age = 100;

console.log(obj2.age);