let weakmap = new WeakMap();

let obj1 = {};
let obj2 = {};

weakmap.set(obj1, 'value1');
weakmap.set(obj2, 'value2');

obj1 = null;

console.log(weakmap.has(obj1));

function Person(name, age) {
  this.name = name;
  this.age = age;
}

Person.prototype.getDetails = function() {
  return this.name + ' is ' + this.age + ' years old.';
};

const john = new Person('John', 25);
console.log(john.getDetails());

const obj1 = { a: 1, b: 2 };
const obj2 = { b: 3, c: 4 };
const mergedObj = { ...obj1, ...obj2 };
console.log(mergedObj);

let person = {
  name: 'Alice',
  age: 30,
  valueOf: function() {
    return this.age;
  }
};

let result = person + 10;
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);

const sym1 = Symbol('description');
const sym2 = Symbol('description');

const obj = {
  [sym1]: 'value1',
  [sym2]: 'value2'
};

console.log(obj[sym1]);

function trickyScope() {
  var x = 10;
  if (true) {
    let x = 5;
    console.log(x);
  }
  console.log(x);
}

trickyScope();