Javascript + dynamic folders

So I have a Javascript function. It is passed a folder name, say "A". This folder contains 5 images which will be picked randomly.

It works well on the page load, as 1 random image appears. But I want it so that when the image is clicked, it is randomized again with an image from the same folder. I tried to go about this with the onmousedown, but it returns a broken image link to file:///C:/Users/StackOverflow/Documents/Website/[object%20HTMLDivElement]/2.jpg

    <script type="text/javascript">
        // <![CDATA[
        function showImage(folder){
            var randomNumber=Math.floor(Math.random()*5);
            docu开发者_Go百科ment.write('<img src="'+folder+'/'+randomNumber+'.jpg" onmousedown="showImage('+folder+')">');
        }
        //]]>   
    </script>

I don't think you really want to be calling document.write() every time the image is clicked. Perhaps you would have more success with a setup like:

<img id="randomImage0" src="" onmousedown="showImage(this, this.lastFolder);" />

<script type="text/javascript">
    function showImage(imgElem, folder){
        var randomNumber=Math.floor(Math.random()*5);
        imgElem.src = folder + '/' + randomNumber + '.jpg";
        imgElem.lastFolder = folder;
    }

    showImage(document.getElementById("randomImage0"), "A");
</script>