app.js

const hamburger = document.querySelector('.header .nav-bar .nav-list .hamburger');
const mobile_menu = document.querySelector('.header .nav-bar .nav-list ul');
const menu_item = document.querySelectorAll('.header .nav-bar .nav-list ul li a');
const header = document.querySelector('.header.container');

hamburger.addEventListener('click' , ()=>{
    hamburger.classList.toggle('active');
    mobile_menu.classList.toggle('active');
})

document.addEventListener('scroll',()=>{
    var scroll_position = window.scrollY;
    if(scroll_position >250){
        header.style.backgroundColor= "black";
    }else{
        header.style.backgroundColor= "transparent";
    }
    
})

menu_item.forEach(item=>{
    item.addEventListener('click',()=>{
        hamburger.classList.toggle('active');
    mobile_menu.classList.toggle('active');
    })
})