JavaScript test

console.log(typeof Object);
console.log(typeof Object());

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

Vehicle.prototype.getWheels = function() {
  return this.wheels;
};

function Car() {
  Vehicle.call(this, 4);
  this.doors = 4;
}

Car.prototype = Object.create(Vehicle.prototype);
Car.prototype.constructor = Car;

const myCar = new Car();
console.log(myCar.getWheels(), myCar instanceof Vehicle);

const a = { x: 1 };
a.__proto__.x = 2;
const b {};

console.log(a.x, b.x);

function* generator() {
  yield* [1, 2];
  yield* (function* () { yield 3; yield 4; })();
}

const gen = generator();

console.log([...gen]);

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

const addTwo = num => num + 2;
const multiplyByThree = num => num * 3;
const subtractTen = num => num - 10;

const calculate = compose(subtractTen, multiplyByThree, addTwo);

console.log(calculate(5));

function* reverseGenerator(arr) {
  for (let i = arr.length - 1; i >= 0; i--) {
    yield arr[i];
  }
}

const result = [...reverseGenerator([1, 2, 3, 4, 5])].join('');

console.log(result);

function mystery() {
  try {
    console.log('A');
    throw new Error('Oops');
    console.log('B');
  } catch (err) {
    console.log('C');
    return 'D';
  } finally {
    console.log('E');
    return 'F';
  }
  console.log('G');
  return 'H';
}

console.log(mystery());

function* infiniteGenerator() {
  let i = 0;
  while (true) {
    yield i++;
  }
}

const weakMap = new WeakMap();
const gen = infiniteGenerator();

weakMap.set(gen, gen.next().value);

const result = weakMap.get(gen) + gen.next().value;

console.log(result);

const users = [
  { id: 1, name: 'Sarah' },
  { id: 2, name: 'Miguel' },
  { id: 3, name: 'Jordan' }
];

const activeUsers = new WeakSet();
activeUsers.add(users[0]);
activeUsers.add(users[2]);

users.splice(1, 1); // Remove Miguel

let count = 0;
for (const user of users) {
  if (activeUsers.has(user)) count++;
}

console.log(count);

async function asyncFunc() {
  console.log('Async Start');
  await new Promise(resolve => setTimeout(resolve, 100));
  console.log('Async End');
}

console.log('Script Start');
asyncFunc();
setTimeout(() => console.log('Timeout 1'), 50);
setTimeout(() => console.log('Timeout 2'), 150);
console.log('Script End');

function createCounter() {
  let count = 0;
  
  return {
    increment() {
      return ++count;
    },
    reset() {
      const oldCount = count;
      count = 0;
      return oldCount;
    }
  };
}

const counterA = createCounter();
const counterB = createCounter();

counterA.increment();
counterA.increment();
counterB.increment();
const result = counterA.reset() + counterB.reset();
console.log(result);

for (var i =0; i < 10; i++){
 setTimeout(function (){
  console.log(i);
 }, 0);
}

const memoryLeak = () => {
  const cache = new Map();
  const weakCache = new WeakMap();
  
  const objKey = { id: 123 };
  const data = { name: 'User data', value: 42 };
  
  cache.set(objKey, data);
  weakCache.set(objKey, data);
  
  // Simulate removing reference to key
  const result = { map: cache.has(objKey), weakMap: weakCache.has(objKey) };
  // objKey = null; // This would be an error, as const can't be reassigned
  
  return result;
};

console.log(memoryLeak());

const obj = { length: 3 };
console.log(Object.keys(obj).length);

const a = [1, 2, 3];
const b = a.slice(0, 2).push(4);
console.log(b);

function createCounter() {
  let count = 0;
  
  function increment() {
    count += 1;
    return count;
  }
  
  function decrement() {
    count -= 1;
    return count;
  }
  
  return { increment, decrement, value: () => count };
}

const counter = createCounter();
counter.increment();
counter.increment();
counter.decrement();

console.log(counter.value() + counter.increment());

var a = 1;

const arrowQuiz = () => {
  console.log(this.a);
};

arrowQuiz();
var a = 2;

const obj = {
  name: 'Taylor',
  greet() {
    return `Hello, ${this.name}!`;
  },
  delayedGreet() {
    setTimeout(function() {
      console.log(this.greet());
    }, 100);
  }
};

obj.delayedGreet();

function* generator1() {
  yield 1;
  yield 2;
}

function* generator2() {
  yield* generator1();
  yield 3;
}

const gen = generator2();
console.log(gen.next().value);
console.log(gen.next().value);
console.log(gen.next().value);

function* rangeGenerator(start, end, step = 1) {
  let current = start;
  while (current <= end) {
    yield current;
    current += step;
  }
}

const numbers = rangeGenerator(1, 10, 2);

numbers.next();
numbers.next();

const values = [...numbers];
console.log(values);