title: jquery dynamically change select option based on another select's value
body: <p>I have two html select dropdowns:</p>
  
  <pre><code>&lt;select name="county" id="county"&gt;
  &lt;option value="Any"&gt;Any County&lt;/option&gt;
  &lt;option value="Lancaster County"&gt;Lancaster County, PA&lt;/option&gt;
  &lt;option value="Berks County"&gt;Berks County, PA&lt;/option&gt;
  &lt;option value="Montgomery County"&gt;Montgomery County, PA&lt;/option&gt;
  &lt;option value="Dauphin County"&gt;Dauphin County, PA&lt;/option&gt;
  &lt;option value="Adams County"&gt;Adams County, PA&lt;/option&gt;
  &lt;option value="Chester County"&gt;Chester County, PA&lt;/option&gt;
  &lt;option value="Lebanon County "&gt;Lebanon County, PA&lt;/option&gt;
  &lt;option value="Delaware County"&gt;Delaware County, PA&lt;/option&gt;
  &lt;option value="York County"&gt;York County, PA&lt;/option&gt;
  &lt;option value="New Castle County"&gt;New Castle County, DE&lt;/option&gt;
  &lt;option value="Orange County"&gt;Orange County, NY&lt;/option&gt;
  &lt;/select&gt;
  
  &lt;select name="township" id="township"&gt;
  &lt;option value="Any"&gt;Any Township&lt;/option&gt;
  &lt;option value="Bethel Township"&gt;Bethel Township&lt;/option&gt;
  &lt;option value="Borough of Cornwall"&gt;Borough of Cornwall&lt;/option&gt;
  &lt;option value="Concord Township"&gt;Concord Township&lt;/option&gt;
  &lt;option value="Cumberland Township"&gt;Cumberland Township&lt;/option&gt;
  &lt;option value="Derry Township"&gt;Derry Township&lt;/option&gt;
  &lt;option value="East Brandywine Township"&gt;East Brandywine Township&lt;/option&gt;
  &lt;option value="East Hempfield Township"&gt;East Hempfield Township&lt;/option&gt;
  &lt;option value="Kennett Township"&gt;Kennett Township&lt;/option&gt;
  &lt;option value="Lower Merion Township"&gt;Lower Merion Township&lt;/option&gt;
  &lt;option value="New Castle County"&gt;New Castle County&lt;/option&gt;
  &lt;option value="Penn Township"&gt;Penn Township&lt;/option&gt;
  &lt;option value="Springfield Township"&gt;Springfield Township&lt;/option&gt;
  &lt;option value="Town of Warwick"&gt;Town of Warwick&lt;/option&gt;
  &lt;option value="Township of Spring"&gt;Township of Spring&lt;/option&gt;
  &lt;option value="Treddyfrin Township"&gt;Treddyfrin Township&lt;/option&gt;
  &lt;option value="Warwick Township"&gt;Warwick Township&lt;/option&gt;
  &lt;option value="West Bradford Township"&gt;West Bradford Township&lt;/option&gt;
  &lt;option value="West Donegal Township"&gt;West Donegal Township&lt;/option&gt;
  &lt;option value="West Lampeter Township"&gt;West Lampeter Township&lt;/option&gt;
  &lt;option value="West Vincent Township"&gt;West Vincent Township&lt;/option&gt;
  &lt;option value="West Whiteland Township"&gt;West Whiteland Township&lt;/option&gt;
  &lt;option value="York Township"&gt;York Township&lt;/option&gt;
  &lt;/select&gt;
  </code></pre>
  
  <p>I need a jquery script that does the following:</p>
  
  <p>When a specific <code>#county option</code> is selected, only the appropriate <code>#township options</code> are displayed.  For example:</p>
  
  <p>If the Lancaster County option is selected, only West Donegal Township, West Lampeter Township, East Hempfield Township, Warwick Township options will be displayed. </p>
  
  <p>Or, if the Berks County option is selected, only Township of Spring will be displayed.  </p>
  
  <p>I've tried other examples of jquery code to make this function work and can't seem to get it to do what I need.  I have little knowledge of jquery/javascript so any help would be appreciated.</p>