Change img height based on div height

Hi everyone,

I am trying to create a script that will change the height of an image to a set value depending on the height of a DIV. Basically, the DIV contains a collapsable table and the img is the page's background. I want the background to re-size based on how much of the table is visible. I hope this isn't too confusing.

Here is my script:

Code:

---

        <script type="text/javascript">
        function setbgsize() {
        var bgimg = document.getElementById('GB');
        var tbh = document.getElementById('FAQtable');
        if(tbh.style.height = '2816px') {
      bgimg.style.height = '1725px';
          }
        else if(tbh.style.height = '1131px') {
      bgimg.style.height = '1025px';
                }
        else if(tbh.style.height = '803px') {
      bgimg.style.height = '825px';
                }
        else if(tbh.style.height = '639px') {
      bgimg.style.height = '500px';
                }
        else(tbh.style.height = '118px') {
      bgimg.style.height = '450px';                     
                }
        }
        </script>

---

Cheers,
Oli.

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