Prototype firstDescendant() Method

Syntax:

element.firstDescendant();

Return Value:

It returns an HTML element

Example:

<html>
<head>
<title>Prototype examples</title>
<script type="text/javascript" 
   src="/javascript/prototype.js">
</script>
<script>

function showResult(){
   desc = $('grandfather').firstDescendant();
   alert("First Descendant is : " 
          + desc.nodeName + ':' + desc.innerHTML );

   child = $('grandfather').firstChild;
   alert("First Child is : " + child.toString() );
}
</script>
</head>

<body>

   <p>Click the button to see the result.</p>

   <div id="grandfather">This is grand father
      <div id="father"> This is father.
         <div id="kid">This is kid</div>
      </div>
   </div>

   <br />
   <input type="button" value="showResult" 
             onclick="showResult();"/>

</body>
</html>

To understand it in better way you can Try it yourself.