How to add the sticky class to the menu while scrolling?

Question

Vue.js

How to add sticky class to menu on scroll using VueJs?
It is necessary to add a menu class when scrolling, so that the menu sticks when scrolling and removed when scrolling to the beginning of the page. How to implement this with VueJs?

window.document.onscroll = () => {
                    let mobileMenu = document.querySelector('mobile-menu');
                    if(window.scrollY > mobileMenu.offsetTop){
                        this.classList.add('sticky')
                    } else {
                        this.classList.remove('sticky');
                    }
                }