tdの中身を取り出したい

javascript 
<html>
<head>
<script type="text/javascript" src="./js/prototype.js"></script>
<script type="text/javascript">
<!--
function editpost(id)
{
    var obj = $(id);
    var obj3 = obj.getElementsByClassName('genre')[0].firstChild;
    alert(obj3.nodeName+","+obj3.nodeType+","+obj3.nodeValue+","+obj3.tagName);
    return false;
}
-->
</script>
</head>
<body>
<table border="1">
<tr id="1234">
<td class="genre">abc</td><td><a href="javascript:;" onclick="editpost('1234');">edit</a></td>
</tr>
</body>
</html>