Vanilla Javascript smooth scroll to element from URL hash - on load or from in page link

gistfile1.txt

/*
    *
    * Smooth Scroll to Anchors
    * */
    const offsetTopScroll = 200;

    //Smooth scroll on page load if anchor is in URL
    if (window.location.hash) {
        const hash = window.location.hash;
        const target = document.getElementById(hash.replace('#', ''));
        if (target) {
            //first scroll to top because browser bounced to anchor at load
            window.scroll({
                top: 0,
                left: 0,
                behavior: 'instant'
            });
            window.scroll({
                top: target.offsetTop - offsetTopScroll,
                left: 0,
                behavior: 'smooth'
            });
        }
    }

    //Smooth scroll to anchor when clicking on a link with #hash
    const anchorLinks = document.querySelectorAll('a[href*="#"]');
    //get site domain
    const domain = window.location.hostname;
    if (anchorLinks) {
        anchorLinks.forEach(link => {
            const hostname = link.getAttribute('href').split('/')[2];
            //check if link is to current site
            if (hostname && hostname === domain) {
                link.addEventListener('click', e => {
                    e.preventDefault();
                    const href = link.getAttribute('href');
                    const url = new URL(href);
                    target = document.getElementById(url.hash.replace('#', ''));
                    if (target) {
                        window.scroll({
                            top: target.offsetTop - offsetTopScroll,
                            left: 0,
                            behavior: 'smooth'
                        });
                        //Update URL with hash because e.preventDefault() prevents default browser behavior
                        history.pushState({}, "", url);
                    }
                });
            }
        });
    }
    /*
    *
    * END: Smooth Scroll to Anchors
    * */