jquery selector for an element MISSING a child element
<p>I am needing help forming a jquery selector to return elements which are missing a particular child element.</p>

<p>Given the following HTML fragment:</p>

<pre><code>    &lt;div id="rack1" class="rack"&gt;
    &lt;span id="rackunit1" class="rackspace"&gt;
        &lt;span id="component1"&gt;BoxA&lt;/span&gt;
        &lt;span id="label1"&gt;Space A&lt;/span&gt;
    &lt;/span&gt;
    &lt;span id="rackunit2" class="rackspace"&gt;
        &lt;span id="label2"&gt;Space B&lt;/span&gt;
    &lt;/span&gt;
    &lt;span id="rackunit3" class="rackspace"&gt;
        &lt;span id="component2"&gt;BoxA&lt;/span&gt;
        &lt;span id="label3"&gt;Space C&lt;/span&gt;
    &lt;/span&gt;
&lt;/div&gt;
&lt;div id="rack2" class="rack"&gt;
    &lt;span id="rackunit4" class="rackspace"&gt;
        &lt;span id="component3"&gt;BoxC&lt;/span&gt;
        &lt;span id="label4"&gt;Space D&lt;/span&gt;
    &lt;/span&gt;
    &lt;span id="rackunit5" class="rackspace"&gt;
        &lt;span id="label5"&gt;Space E&lt;/span&gt;
    &lt;/span&gt;
    &lt;span id="rackunit6" class="rackspace"&gt;
        &lt;span id="component4"&gt;BoxD&lt;/span&gt;
        &lt;span id="label6"&gt;Space F&lt;/span&gt;
    &lt;/span&gt;
&lt;/div&gt;
</code></pre>

<p>Find for me the rackunit spans with NO component span.
Thus far I have:
$(".rack .rackspace") to get me all of the rackunit spans, not sure how to either exclude those with a component span or select only those without one...</p>
