var vfa_html = document.getElementsByTagName("html")[0];
vfa_html.setAttribute("id", "vfa_html_anchor");
// console.log(vfa_html);
var vfa_topButton = document.getElementById('vfa_topButton');

function vfa_topButton_function() {
    if (window.matchMedia("(max-width: 767px)").matches) {

        if (window.scrollY > 1500) {
            vfa_topButton.style.opacity = 1;
        } else {
            vfa_topButton.style.opacity = 0;
        }

    } else {
        if (window.scrollY > 1000) {
            vfa_topButton.style.opacity = 1;
        } else {
            vfa_topButton.style.opacity = 0;
        }
    }
}

document.addEventListener('scroll', function () {
    //console.log(scrollY);
    vfa_topButton_function();
});