let timer = null;
function scroll() {
let top = Math.max(document.body.scrollTop, document.documentElement.scrollTop);
if (top > 0) {
window.scrollBy(0, ((top + 100) / -10));
timer = setTimeout(function() {
scroll();
}, 20);
} else {
clearTimeout(timer);
}
return false;
}
scroll();
https://jsfiddle.net/yarkov_aleksei/fxs215kd/
form_email.addEventListener("submit",function(event){
event.preventDefault();
return false;
});