const body = document.body,
scrollWrap = document.getElementsByClassName("wrapper_class")[0],
height = scrollWrap.getBoundingClientRect().height -1,
speed = 0.04;
var offset = 0;
body.style.height = Math.floor(height) + "px";
function smoothScroll() {
offset += (window.pageYOffset - offset) * speed;
var scroll = "translateY(-" + offset + "px) translateZ(0)";
scrollWrap.style.transform = scroll;
}