Ajax实现局部刷新

Ajax实现局部刷新

    <script type="text/javascript">
    var xmlhttp;
    function getData()
    {
      //获取用户填写的名称
      var city=document.getElementByIdx("txt").value;
      //建立异步调用对象
      xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
      //将对象状态与事件相关联
      xmlhttp.onreadystatechange=statechange;
      //加载要连接的页面
      xmlhttp.Open("POST","datapage.aspx?city=" +city,true);
      //发送请求
      xmlhttp.Send();
    }
    function statechange()
    {
      //判断异步调用是否已经完成
      if(xmlhttp.readystate==4)
      {
        //判断完成的提示代码是不是OK状态
        if(xmlhttp.status==200)
        {
           //将返回数据做为参数，传递给填充方法
           FillData(xmlhttp.responseText);
        }
      }
    }
    function FillData(strcity)
    {
       document.getElementByIdx("DropDownList1").options.length=0;
       var indexofcity;
       var city;
       //切割传递来的字符串
       while(strcity.length>0)
       {
       //判断是不是最后一个字符串
        indexofcity=strcity.indexOf(",");
        if(indexofcity >0)
        {
        city=strcity.substring(0,indexofcity);
        strcity=strcity.substring(indexofcity+1);
        //填充下拉框
        document.getElementByIdx("DropDownList1").add(new Option(city,city));
        }