sticky.js

var el = document.querySelector(".shopper-top-menu");
var elOriginal = el.offsetTop
window.addEventListener("scroll" , function(e){
  if( window.scrollY >= el.offsetTop ) {
    document.body.style.paddingTop = el.offsetHeight;
    el.style.position = "fixed";
    el.classList.add("fixed")
    el.style.width = "100%";
    el.style.top = 0;
    el.style.left = 0 ;
    el.style.zIndex = 100;
  } 
  if(window.scrollY < elOriginal) {
    document.body.style.paddingTop = 0;
    el.classList.remove("fixed")
    el.style.position = "relative";
    el.style.width = "100%";
    el.style.zIndex = 100;
  }
})