Prototype readAttribute() Method

Syntax:

element.readAttribute(attribute);

Return Value:

Returns the value of element's attribute or null if attribute has not been specified.

Example:

<html>
<head>
<title>Prototype examples</title>

<script type="text/javascript" 
   src="/javascript/prototype.js">
</script>
<script>

function showResult(){
   var str = $('tag').readAttribute('href');
   alert("Value of href : " + str );

   var str = $('tag').readAttribute('title');
   alert("Value of title : " + str );

   var str = $('tag').readAttribute('somethingelse');
   alert("Value ofsomething else : " + str );

}

</script>
</head>

<body>

  <p>Click the button to see the result.</p>
  
  <a id="tag" href="/tags/prototype" rel="tag" 
		title="view related bookmarks.">Prototype</a>
  
  <br />
  <br />
  <input type="button" value="Show Result" onclick="showResult();"/>

</body>
</html>

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