JavaScript calculate percentage when user scroll web page

http://thy4u.blogspot.com

by Vuthy Sok

HTML

<div id="percentage"></div>
<div style="height: 4000px;"></div>

CSS

#percentage
{
    position: fixed;
}

JavaScript

window.onscroll = function(){ 
        var heightOfWindow = window.innerHeight;
        var contentScrolled = window.pageYOffset;
        var bodyHeight = window.document.getElementsByTagName("body")[0].offsetHeight;
        if(bodyHeight - contentScrolled <= heightOfWindow)
       {
           window.document.getElementById("percentage").innerHTML = "100%";
       }
       else
       {
           var total = bodyHeight - heightOfWindow;
           var got = contentScrolled;
           window.document.getElementById("percentage").innerHTML = parseInt((got/total) * 100) + "%";
       }
   }