function Person() {}

var person = new Person();

console.log(person instanceof Person);
console.log(person instanceof Object);

var foo = {};
var bar = Object.create(foo);

foo.a = 1;

console.log(bar.a);

try {
  try {
    // Creating a custom error type
    class CustomError extends Error {
      constructor(message) {
        super(message);
        this.name = "CustomError";
      }
    }
    
    const fn = () => {
      throw new CustomError("Something went wrong");
    };
    
    try {
      fn();
    } catch (e) {
      throw new TypeError("Type error occurred");
    }
  } catch (e) {
    console.log(e instanceof Error, e.name, e instanceof TypeError);
  }
} catch (e) {
  console.log("Outer catch", e.message);
}

console.log(1 + 2 + '3' - 4 + 5);

const createAsyncFunction = (ms, result) => async () => {

await new Promise(resolve => setTimeout(resolve, ms));
return result;

18
[

createAsyncFunction(1000, "A"),

const asyncFunctions

(
createAsyncFunction(500, "B"),
createAsyncFunction(2000, "C"),

Ig

Promise. race(asyncFunctions.map( func =>
func())).then(result => console.log(result));

function* counter() {
  let i = 1;
  while (true) {
    const reset = yield i++;
    if (reset) {
      i = 1;
    }
  }
}

const gen = counter();
console.log(gen.next().value);
console.log(gen.next().value);
console.log(gen.next(true).value);
console.log(gen.next().value);

let obj = { a: 1 };
Object.freeze(obj);

console.log(Object.isFrozen(obj));
console.log(obj.a = 2);
console.log(obj.a);

function Animal() {}

function Dog() {}

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

const rover = new Dog();

console.log(rover.constructor === Animal);

const users = [
  { id: 1, name: 'Alice' },
  { id: 2, name: 'Bob' },
  { id: 3, name: 'Charlie' }
];

const userScores = new WeakMap();

// Set scores for users
userScores.set(users[0], 95);
userScores.set(users[1], 80);

// Remove reference to Bob
users[1] = null;

let sum = 0;
for (const user of users) {
  if (user && userScores.has(user)) {
    sum += userScores.get(user);
  }
}

console.log(sum);

const promise = new Promise((resolve, reject) => {
  setTimeout(() => resolve(3), 1000);
});

promise
  .then(result => {
    console.log(result);
    return result * 2;
  })
  .then(result => {
    console.log(result);
    return new Promise(resolve => setTimeout(() => resolve(result * 3), 1000));
  })
  .then(result => {
    console.log(result);
  });

var arr=[1,2,3,4,5];
console.log(arr.map((prev,curr)=>prev+curr));
console.log(arr.reduce((a,b)=>a+b));
console.log(arr.filter((a,b)=> (a + b) <= 5));

class ShoppingCart {
  constructor() {
    if (ShoppingCart.instance) {
      return ShoppingCart.instance;
    }
    
    this.items = [];
    ShoppingCart.instance = this;
  }
  
  addItem(item) {
    this.items.push(item);
  }
  
  getItems() {
    return [...this.items];
  }
}

const cart1 = new ShoppingCart();
const cart2 = new ShoppingCart();

cart1.addItem('Book');
cart2.addItem('Laptop');

console.log(cart1.getItems());

const obj = {};
Object.defineProperty(obj, 'name', {
  value: 'Alice',
  writable: false,
  configurable: false
});

try {
  obj.name = 'Bob';
  delete obj.name;
  console.log(obj.name);
} catch (e) {
  console.log('Error:', e.message);
}

const team = {
  lead: { name: 'Alice', projects: ['Alpha', 'Beta'] },
  dev: { name: 'Bob', projects: ['Gamma'] },
  tester: { name: 'Charlie', projects: [] }
};

const { 
  lead: { projects: [leadProject] },
  dev: { projects: [devProject = 'Delta'] },
  tester: { projects: [testerProject = 'Epsilon'] }
} = team;

console.log(`${leadProject}-${devProject}-${testerProject}`);

const wMap = new WeakMap();

function foo() {
   wMap.set(this, 1);
};
const bar = () => wMap.set(this, 2);

bar();
foo();

console.log(wMap.get(this));

const asyncFunction = async () => {
  const delay = (ms) => new Promise(resolve => setTimeout(resolve, ms));

  const result = await Promise.race([delay(100), delay(500)]);
  return result;
};

asyncFunction().then(value => console.log(value));

const target = { a: 1, b: 2 };
const handler = {
  get(obj, prop) {
    return prop in obj ? obj[prop] * 2 : 'not found';
  },
  set(obj, prop, value) {
    if (typeof value !== 'number') {
      return false;
    }
    obj[prop] = value + 10;
    return true;
  }
};

const proxy = new Proxy(target, handler);
proxy.c = '5';
proxy.d = 5;

console.log(JSON.stringify({
  a: proxy.a,
  b: proxy.b,
  c: proxy.c,
  d: target.d,
  hasC: Reflect.has(target, 'c')
}));

var a = ( function a() {
   return '1';
},
function b() {
   return 2;
})()
alert(typeof a)

function Foo() {
  this.bar = 1;
}

Foo.prototype.bar = 2;

const foo = new Foo();
console.log(foo.bar);