title: get value of an attribute of the clicked element
body: <pre><code>&lt;ul id='langs'&gt;
     &lt;li data-val='en'&gt;english&lt;/li&gt;
     &lt;li data-val='fr'&gt;francais&lt;/li&gt;
     &lt;li data-val='it'&gt;italiano&lt;/li&gt;
  &lt;/ul&gt;
  </code></pre>
  
  <p>when the user clicks on any of these <code>&lt;li&gt;</code> I want to <code>alert()</code> it's data-val attribute value</p>
  
  <p>anybody knows how?</p>