function* numberGenerator() {
  yield 1;
  yield 2;
  yield 3;
}

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

const symbol1 = Symbol('symbol');
const symbol2 = Symbol('symbol');

const obj = {};
obj[symbol1] = 'value1';
obj[symbol2] = 'value2';

console.log(obj[symbol1]);

function outerFunction() {
  let x = 10;
  function innerFunction() {
    x += 5;
    console.log(x);
  }
  return innerFunction;
}

const closureFunc = outerFunction();
closureFunc();
closureFunc();

const promise = new Promise((resolve, reject) => {
  reject('Error occurred');
});

promise
  .then(() => {
    console.log('Promise resolved!');
  })
  .catch(error => {
    console.log(error);
  })
  .then(() => {
    console.log('Process completed');
  });

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);