Get element percent in viewport

gistfile1.txt

_getPercentInView = function(element){
    $element = $(element);

    var pos                     = $element.offset(),
        theViewport             = {top:null, left:null, bottom:null, right:null, width:null, height:null},
        theElement              = {top:null, left:null, bottom:null, right:null, width:null, height:null},
        elemLeft                = pos.left,
        elemTop                 = pos.top,
        elemHeight              = $element.height(),
        elemWidth               = $element.width();

    theViewport.width       = $(window).width();
    theViewport.height      = $(window).height();
    theViewport.top         = $(window).scrollTop();
    theViewport.left        = $(window).scrollLeft();
    theViewport.bottom      = theViewport.top+theViewport.height;
    theViewport.right       = theViewport.left+theViewport.width;

    theElement.top          = elemTop - theViewport.top;
    theElement.left         = elemLeft - theViewport.left;
    theElement.width        = elemWidth;
    theElement.height       = elemHeight;
    theElement.bottom       = theElement.top+theElement.height;
    theElement.right        = theElement.left+theElement.width;

    var nPercentInView = Math.round(100 * ((theElement.height-(Math.max(0,0-theElement.top) + Math.max(0,theElement.bottom-theViewport.height))) / theElement.height) * ((theElement.width-(Math.max(0,0-theElement.left) + Math.max(0,theElement.right-theViewport.width))) / theElement.width)   );
    return nPercentInView;
}