我用纯js也实现了，可是老是出现上面的问题，怎么解决呢？代码如下：

function Class1_Changed(pid)
{
document.getElementById("Class2").length = 0;
document.getElementById("Class2").options[0] = new Option('二级分类','0');

//连接数据库
if(pid!="0")
{
var conn = new ActiveXObject("ADODB.Connection");
conn.Open("Provider=SQLOLEDB.1; Data Source=.; User ID=sa; Password=; Initial Catalog=数据库名");
var rs = new ActiveXObject("ADODB.Recordset");
var sql="select ID,Title from ProClass where PID='"+pid+"'";
rs.open(sql, conn);

while (!rs.EOF)
{
document.getElementById("Class2").options[document.getElementById("Class2").length] = new Option(rs("Title"), rs("ID"));
rs.moveNext;
}

rs.close();
rs = null;
conn.close();
conn = null;
}
}