Is assigment simultaneous to indexing valid?
<p>I just discovered this line and I'm wondering if it's valid code. Please note that I don't wonder what it does - that's obvious. I just want to know if it's OK code, academically speaking (and by that I mean that its validity lies in compliance to a standard or at least a generally accepted practice). I know it works in the browsers it needs to.</p>

<pre><code>target.src = urls[index = ++index % urls.length];
</code></pre>
