jquery: find common elements in 2 sets of divs
<p>For a markup like this:</p>

<pre><code>&lt;div id="set1"&gt;
 &lt;div id="100"&gt;a div&lt;/div&gt;
 &lt;div id="101"&gt;another div&lt;/div&gt;
 &lt;div id="102"&gt;another div 2&lt;/div&gt;
 &lt;div id="120"&gt;same div&lt;/div&gt;
&lt;/div&gt;  

&lt;div id="set2"&gt;
 &lt;div id="105"&gt;a different div&gt;
 &lt;div id="101"&gt;another div&lt;/div&gt;
 &lt;div id="110"&gt;more divs&lt;/div&gt;
 &lt;div id="120"&gt;same div&lt;/div&gt;
&lt;/div&gt;
</code></pre>

<p>As you can see both #set1 and #set2 contain 2 divs with the same id (101, 120). Is it possible somehow with jQuery to find the common elements and add a class to the divs in #set1 that have the same id with divs in #set2?</p>

<p>In other words after the script run the above code would look like this:</p>

<pre><code>&lt;div id="set1"&gt;
 &lt;div id="100"&gt;a div&lt;/div&gt;
 &lt;div id="101" class="added"&gt;another div&lt;/div&gt;
 &lt;div id="102"&gt;another div 2&lt;/div&gt;
 &lt;div id="120" class="added"&gt;same div&lt;/div&gt;
&lt;/div&gt;  

&lt;div id="set2"&gt;
 &lt;div id="105"&gt;a different div&gt;
 &lt;div id="101"&gt;another div&lt;/div&gt;
 &lt;div id="110"&gt;more divs&lt;/div&gt;
 &lt;div id="120"&gt;same div&lt;/div&gt;
&lt;/div&gt;
</code></pre>

<p><strong>EDIT</strong>
playing around with it i did something but i am not sure it can go anywhere. I created an array with the ids in both sets and in Firebug i can see an array with the values</p>

<pre><code> var arrEl = [];
   $('#set1 div, #set2 div').each( function(index) {
    var id = $(this).attr('id');            
    arrEl.push(id);

 //maybe somehow check the array for the values that appear twice, and add the class to the //matching divs?
   });
</code></pre>
