const numbers = [1, 2, 3, 4, 5];

const result = numbers
  .filter(n => n % 2 === 0)
  .map(n => n * 2)
  .reduce((acc, n) => acc + n, 0);

console.log(result);

var str="example";
var result=str.replace("e","@");
console.log(result);

const items = new WeakSet();
const obj1 = { id: 1 };
const obj2 = { id: 2 };

items.add(obj1);
items.add(obj2);

obj2.value = 'test';
console.log(items.has(obj2));

obj2 = null;
setTimeout(() => {
  console.log(items.has(obj2));
}, 0);

function Person(name) {
  this.name = name;
}
Person.prototype.greet = function() {
  return `Hello, my name is ${this.name}`;
};
const john = new Person('John');
console.log(john.greet());

var arr=[[9,0],[5,3],[2,6],[7,8]];
var result=[];
for (var i=0;i<arr.length;i++) 
  result=result.concat(arr[i]);
console.log(result.sort());

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

function trickyScope() {
    let x = 10;
    if (true) {
        let x = 20;
        console.log(x); // A
    }
    console.log(x); // B
    {
        let x = 30;
        console.log(x); // C
    }
    console.log(x); // D
}

trickyScope();

const person = {
  name: 'Alice',
  age: 25,
  city: 'Wonderland'
};

const additionalInfo = {
  age: 30,
  occupation: 'Explorer'
};

const combined = {
  ...person,
  ...additionalInfo
};

console.log(combined.age);

const numbers = [1, 2, 3, 4, 5];

const result = numbers
  .filter(n => n % 2 === 0)
  .map(n => n * 2)
  .reduce((acc, n) => acc + n, 0);

console.log(result);

const compose = (...fns) => fns.reduce((f, g) => (...args) => f(g(...args)));

const pipe = (...fns) => fns.reduce((f, g) => (...args) => g(f(...args)));

const double  = x => x * 2;
const addTen  = x => x + 10;
const square  = x => x * x;
const negate  = x => -x;

const transform1 = compose(negate, square, addTen, double);
const transform2 = pipe(double, addTen, square, negate);

const val = 3;

console.log(transform1(val), transform2(val));

const numbers = [1, 2, 3, 4, 5];

const result = numbers
  .filter(n => n % 2 === 0)
  .map(n => n * 2)
  .reduce((acc, n) => acc + n, 0);

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);

function capIt(str){
  return str.split(/ /)
            .map(s=>s.replace(/^./,x=>x.toUpperCase()))
            .join(" ")
}
console.log( capIt("hello world!"))  
console.log( capIt("my name is John."))

const map = new Map();
const key1 = {};
const key2 = key1;

map.set(key1, "Value for key1");
map.set(key2, "Value for key2");

console.log(map.get(key2));
console.log(map.get(key1));

const map = new Map();
const key1 = {};
const key2 = key1;

map.set(key1, "Value for key1");
map.set(key2, "Value for key2");

console.log(map.get(key2));
console.log(map.get(key1));

function Animal(name) {
  this.name = name;
}

Animal.prototype.speak = function() {
  return `${this.name} makes a noise`;
};

function Dog(name) {
  Animal.call(this, name);
}

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

Dog.prototype.speak = function() {
  return `${this.name} barks`;
};

const animal = new Animal('Animal');
const dog = new Dog('Rex');

console.log(dog instanceof Animal);

async function asyncChain() {
   const values = [2, 3, 5, 7, 0];
   const total = await values.reduce(async (acc, values) => {
      const current = await acc;
      return current * values;
   }, Promise.resolve(1));
   return total;
}

asyncChain().then(result => console.log(result));

const operations = {
  add: (a, b) => a + b,
  subtract: (a, b) => a - b,
  multiply: (a, b) => a * b,
  divide: (a, b) => b !== 0 ? a / b : null,
};

const pipeline = (...fns) => (value) => fns.reduce((acc, fn) => fn(acc), value);

const double  = (x) => operations.multiply(x, 2);
const addTen  = (x) => operations.add(x, 10);
const halve   = (x) => operations.divide(x, 2);
const subtractThree = (x) => operations.subtract(x, 3);

const transform = pipeline(double, addTen, halve, subtractThree);

console.log(transform(5));

const numbers = [1, 3, 5, 7, 13];

const result = numbers.reduce((acc, val) => {
  acc[val] = val * 2;
  return acc;
}, {});

console.log(result);

const numbers = [1, 2, 3, 4, 5, 6];

const result = numbers.reduce((acc, num) => {
  if (num % 2 === 0) {
    acc.even += num;
  } else {
    acc.odd *= num;
  }
  return acc;
}, { even: 1, odd: 1 });

console.log(result);

var i = 5;

const arr = new Array(5);
arr.forEach(() => i++);

console.log(i);