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

I'm using a function to make it cross-browser compatible that can be found here: Cross-browser method for detecting the scrollTop of the browser window

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

if(!getScrollTop()){
   // user is at the top
}

Here is a little demo: http://jsfiddle.net/uDS4n/1/