object required js error

Helllo Friends,
below is my jsp

<%@ taglib uri="/WEB-INF/lib/struts-html.tld" prefix="html" %>
<%@ taglib uri="/WEB-INF/lib/struts-logic.tld" prefix="logic" %>
<%@ taglib uri="/WEB-INF/lib/struts-bean.tld" prefix="bean" %>
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<script type="text/javascript">
function fun(obj,idx){
alert("portfolio id is "+obj+' at row no'+idx);
document.getElementById('nodeIterator[idx]');
//alert(document.getElementById('nodeIterator[idx].name').value);
}
</script>
<head>

<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>page2</title>

</head>
<body>
<form action="dummys.do" method="post">
<%--<bean:define id="portIdOfNode" name="node" property="portId"></bean:define>--%>
<bean:define id="port" name="myform" property="listOfPortfolio"></bean:define>
<h1>Drop down page </h1>
<bean:define id="selPort" name="myform" property="listOfPortfolio"></bean:define>
<table border="1" background="yellow" bgcolor="yellow">
<th>node</th>
<th>portfolio</th>
<logic:iterate id="nodeIterator" name="myform" property="listOfNode" indexId="idx">
<tr>
<td>
<%--<bean:write name="node" property="nodeName"/> --%>
<bean:write name="nodeIterator" property="nodeName"/>
</td>
<td><%=idx %>

portfolio<html:select name="nodeIterator" property="nodeIterator[<%=idx %>].portId" onclick='<%="fun(this.value,"+idx+")" %>' value="<bean:write name='nodeIterator' property='portId'>" multiple="true" indexed="true" >
<html:optionsCollection property="listOfPortfolio" name="myform" label="portfolioName" value="portfolioId" ></html:optionsCollection>
</html:select>
</td>

</tr>
</logic:iterate>
</table>
submit here:<input type="submit" onclick="">

</form>
</body>

</html>

I get an error in the only javascript method when I try getting the value of nodeIterator.

Please help!

Thanks
Faisal