Explain why scrollTop() always returns 0 here

Question

See http://codepen.io/anon/pen/NGqPNz

CSS:

html {
  height: 100%;
  overflow-y: hidden;
}
body {
  height: 100%;
  overflow-y: auto;
}

Answer 1

It's because you have overflow-y: hidden;. Remove this and then scrollTop() will work