how to hide dropdown on scrolling

  /* When the user scrolls down, hide the navbar. When the user scrolls up, show 
  the navbar */
var prevScrollpos = window.pageYOffset;
window.onscroll = 
  function() {
  var currentScrollPos = window.pageYOffset;
  if 
  (prevScrollpos > currentScrollPos) {
    
  document.getElementById("navbar").style.top = "0";
  } else {
    
  document.getElementById("navbar").style.top = "-50px";
  }
  
  prevScrollpos = currentScrollPos;
} 

window.onsrcoll = function(){
     var position = 0;
     var scPos = (this.pageYOffset || document.documentElement.scrollTop) - (document.documentElement.clientTop || 0);
     position += scPos;
     if(position > scPos) {
      // code here to hide drop-down menu.
     }
    }