title: jquery selector efficiently
body: <pre><code>&lt;div id="parent"&gt;
      &lt;div id="child"&gt;&lt;/div&gt;
  &lt;/div&gt;
  &lt;!-- script --&gt;
  &lt;script type="text/javascript"&gt;
      var $parent = $("#parent");
      //$parent().dosomething()   
      // ... use $parent do something
  
      //!!! now i want use child !!!
      var $child = $parent.find("#child"); //method  one
      var $child = $("#child");           //method two
      //$child().dosomething()  
  &lt;/script&gt;
  </code></pre>
  
  <p>Question: method one  or  method two is better ??(hope explanation in detail ,thanks!)</p>
  
  <p>waiting for your help</p>