title: How to get length of elements with a certain css attribute?
body: <p>If i have an html snippet </p>
  
  <pre><code>&lt;div&gt;
       &lt;ul style="display:block"&gt;
           &lt;li&gt;A&lt;/li&gt;
           &lt;li&gt;B&lt;/li&gt;
       &lt;/ul&gt;
       &lt;ul style="display:none"&gt;
           &lt;li&gt;&lt;/li&gt;
           &lt;li&gt;&lt;/li&gt;
       &lt;/ul&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>How to use jQuery to find the no. of ul elements in div with a css property of <code>display: none</code>?
  I know I can use <code>$('div').children('ul').length</code> but this returns all ul elements</p>