js/jquery循环提取table单元格值

<table id="tbitem">
    <tr><td>测试数据1</td></tr>
    <tr><td>测试数据2</td></tr>
    <tr><td>测试数据3</td></tr>
    <tr><td>测试数据4</td></tr>
    <tr><td>测试数据5</td></tr>
    <tr><td>测试数据6</td></tr>
</table>
<script type="text/javascript">
    var table = document.getElementById("tbitem"); 
    var td = table.getElementsByTagName("td");
    var len = td.length;
    for(i=0;i<len;i++){
        alert(td[i].innerHTML);
    } 
</script>

jquery 版的
$(document).ready(function(){
var st1r="";
$("td").each(function(){ st1r+=$(this).html()+",";alert( st1r)})
});
这个是通过判断里面是否有td ，如果有td，都提取里面的值

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>untitle</title>
<script>
    window.onload=function(){
        var b=document.getElementsByTagName('td').length;
        for(var i=1;i<=b;i++){
            var a=document.getElementById('a'+i);
            alert(a.innerHTML);
        }
    }
</script>
</head>
<body>
    <table>
        <tr>
            <td id="a1">aa</td>
            <td id="a2">bb</td>
            <td id="a3">cc</td>
        </tr>
    </table>
</body>
</html>