javascript - Get height of non-overflowed portion of div

Question

Say I have a wrapper div with a overflow:hidden on it and a div inside that that spans far below the visible portion. How can I get the visible height of the internal div?

<div id="wrapper" style="overflow: hidden; height:400px;">
    <div id="inner">
        <!--Lots of content in here-->
    </div>
<div>

Every method I try attempting to get the height of the inner div returns the complete height including the hidden parts, i.e. 2000px. I want to be able to get the height of only the visible portion, so 400px in this example case.

I know I could just get the height of the parentNode, but in production, the inner div might not be a first child. So there might be other divs separating them, and so the height of #inner would be 400 - whatever the offsets of the elements between it and #wrapper.

Answer 1

As basic algorithm this could work:

var offset = 0;
var node = document.getElementById("inner");
while (node.offsetParent && node.offsetParent.id != "wrapper")
{
    offset += node.offsetTop;
    node = node.offsetParent;
}
var visible = node.offsetHeight - offset;

But if you're doing these kinds of things, maybe you already use jQuery, which might be of service with its .height() and .offset() functions:

$("#wrapper").height()-
$("#inner").offset()['top']+
$("#wrapper").offset()['top'];