js实现前台动态添加文本框，后台获取文本框内容

%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
< !DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" >

< html >
< title >
</title>
< head >
</head>
< body >
< form id ="form1" action ="request.jsp" >
< script language ="javascript" type ="text/javascript" >

var count=0 ;
function additem(id)
{
    var row,cell,str;
    row = document.getElementById(id).insertRow();
    if(row != null )
    {
cell = row.insertCell();
cell.innerHTML=" < input id=\"St"+count+"\" type=\"text\" name=\"St"+count+"\" value= \"St"+count+"\" > < input type=\"button\" value=\"删除\" onclick=\'deleteitem(this);\' >";
count ++;
    }
}
function deleteitem(obj)
{
    var curRow = obj.parentNode.parentNode;
    tb.deleteRow(curRow.rowIndex);
}

function getsub()
{
var re="";
for (var    i = 0 ;i<count;i++)
{
re += document.getElementsByName("St"+i)[0].value;

}
document.getElementById("Hidden1").value=re;
}


</script> < table id ="tb" > </table>
< input name ="button" type ="button" onclick ='additem("tb")' value="添加 >>"/> < input type ="submit" name ="submit" onclick ="getsub()" value ="提交" />
         < input id ="Hidden1" name ="Hidden1" type ="hidden" value="" />
         </form>
</body>

</html>