get info on table click
<p>my table has the following html</p>

<pre><code>&lt;table class="tb" id="tb1"&gt;
&lt;tr&gt;
&lt;th scope="col"&gt;OrderID&lt;/th&gt;
&lt;th scope="col"&gt;ProductName&lt;/th&gt;
&lt;th scope="col"&gt;Quantity&lt;/th&gt;
&lt;/tr&gt;
&lt;tr&gt;....&lt;/tr&gt;
</code></pre>

<p>When i click only on either OrderID, ProductName or Quantity i.e heading, I want to apply a css class to entire column.</p>
