title: using variables within a jquery selector
body: <p>I'm trying to build a dynamic jquery selector with the following code:</p>
  
  <pre><code>var section_id = "{segment_3}";
  var num_children = $('#'+ section_id + ' ul').children().size();
  </code></pre>
  
  <p>where segment_3 is a value I successfully retrieve from the url string, which, for example, might return the value of "section_one"</p>
  
  <p>But when trying to create the variable num_children, this reference doesn't work. How do I construct the code to build a dynamic reference? Thanks for any help.</p>