How can the "Impossibly Simple Image Randomizer with jQuery" be accomplished.. without jQuery
<p>I'd like to inject a random <code>background-image</code> into a div. I <a href="http://briancray.com/posts/simple-image-randomizer-jquery/" rel="nofollow">came across</a> the following code which does this perfectly using the jQuery library:</p>

<p><strong>Sets the array of images:</strong></p>

<pre><code>var images = ['image1.jpg', 'image2.jpg', 'image3.jpg', 'image4.jpg', 'image5.jpg'];
</code></pre>

<p><strong>Sets the div for the random background using previously defined array:</strong></p>

<pre><code>$('#div').css({'background-image': 'url(images/' + images[Math.floor(Math.random() * images.length)] + ')'});
</code></pre>

<p>Here's the thing - I'd like to do this without having to load the jQuery library. I like the simplicity of the above code, but I'm new to the Javascript language and I don't know to reformat this for use without jQuery.</p>

<p>I've spent some time looking for Javascript alternatives to the above code, but they're all relatively lengthy or unnecessarily "busy". Any help on this is much appreciated.</p>
