Smooth vertical scrolling on mouse wheel in vanilla javascript?

Question

I am a huge fan for vanilla javascript, currently I am working on a project where I need to implement smooth scrolling on mouse wheel scroll. I want to implement this using

Answer 1

A pure JavaScript onscroll event will work:

var container = document.getElementById('myScrollingSurface');
var lastY = 0;
container.onscroll = function () {
  doSomethingCool(container.scrollTop - lastY);
  lastY = container.scrollTop;
};