javascript - How do i detect when a user is at the top of the webpage

Question

I\'m pretty much completely new to javascript, and I know there\'s already a similar question to this on here, but i would like the script as in.

if (user is at top of

Answer 1

This is a little snippet I use to determine the scrolltop of a page, I can't remember where I got it, or whether I wrote it myself so can't credit it.

var st=0;
if(typeof pageYOffset!= 'undefined'){
    //most browsers
    st = pageYOffset;
} else {
    var B = document.body; //IE 'quirks'
    var D = document.documentElement; //IE with doctype
    D = (D.clientHeight)? D: B;
    st = D.scrollTop;
}

if st==0 then the user is at the top of the page!