Prototype identify() Method

Syntax:

element.identify();

Return Value:

Returns HTML element ID

Example:

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

function showResult(){
   var str = $('apple').identify();
   alert("Apple's ID: " + str );
   var str = $('apple').next().identify()
   alert("Orange's ID: " + str );
}
</script>
</head>

<body>

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

  <ul>
   <li id="apple">apple</li>
   <li>orange</li>
  </ul>

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

</body>
</html>

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