为什么全局变量 没有赋值成功（或者说又被刷回初值了？）


<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Ajax_ParseXML.aspx.cs" Inherits="AllDemos.Ajax_ParseXML" %><!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 runat="server">
    <title>无标题页</title>
        <script type="text/javascript">
        var xmlHttp;
        var requestType='qwe';
        function createXMLHttpRequest(){
            if(window.ActiveXObject)
                xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
            else if(window.XMLHttpRequest)
                xmlHttp=new XMLHttpRequest();
        }
        function startRequest(requestList){    
             //alert('startRequest...');
            requsetType=requestList;
            alert(requsetType);
            createXMLHttpRequest();
            xmlHttp.onreadystatechange=handleStateChange; 
            alert(requsetType);
            xmlHttp.open("GET","Ajax_ParseXML.xml",true);
            xmlHttp.send(null);           
        }
        function handleStateChange(){
              alert(requestType); 
              if(xmlHttp.readyState==4)
                if(xmlHttp.status==200){
                    if(requestType=="north")
                       listNorthStates();
                    else if(requestType=="all")
                       listAllStates();    
                }
                   
        }
        function listNorthStates(){
            //alert('listNorthStates...');
            var xmlDoc=xmlHttp.responseXML;
            var northNode=xmlDoc.getElementsByTagName("north")[0];
            var out ="Northern States";
            var northStates=northNode.getElementsByTagName("state");
            outputList("Northern States",northStates);
        }
        function listAllStates(){
            //alert('listAllStates...');
            var xmlDoc=xmlHttp.responseXML;
            var allStates=xmlDoc.getElementsByTagName("state");
            outputList("All States in Document",allStates);
        }
        function outputList(title,states){
            var out = title ;
            var currentState=null;
            for(var i=0;i<states.length;i++){
                currentState=states[i];
                out=out +"\n-"+currentState.childNodes[0].nodeValue;
            }
            alert(out);
        }
    </script>
</head>
<body>
    <form id="form1" runat="server">
    <div>
    <h1>Proecss XML Document of U.S States</h1>
    <input type="button" value="View All Listed States" onclick="startRequest('all')" />
    <input type="button" value="View All Listed Northern States" onclick="startRequest('north')" />
    </div>
    </form>
</body>
</html>

解决方案 »

  1.   

    呵呵 ，不好意思啊。   
    function handleStateChange(){
                  alert(requestType);               if(xmlHttp.readyState==4)
                    if(xmlHttp.status==200){
                        if(requestType=="north")
                           listNorthStates();
                        else if(requestType=="all")
                           listAllStates();    
                    }
                       
            }
    主要问题是在requestType，在startRequest(requestList)函数中已经赋值了，但是到handleStateChange()函数中时，值又变为初始值了！全局变量啊！！!页面不刷新！！！跪求问题了！
      

  2.   

    <script type="text/javascript">
            var xmlHttp;
            //var requestType='qwe';
            function createXMLHttpRequest(){
                if(window.ActiveXObject)
                    xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
                else if(window.XMLHttpRequest)
                    xmlHttp=new XMLHttpRequest();
            }
            function startRequest(requestList){  
                 //alert('startRequest...');
                var requsetType=requestList;            createXMLHttpRequest();
                xmlHttp.open("GET","Ajax_ParseXML.xml"+new Date().getTime(),true);
                xmlHttp.onreadystatechange=handleStateChange(requsetType); 
                alert(requsetType);
               
                xmlHttp.send(null);           
            }
            function handleStateChange(requestType){
                  alert(requestType); 
                  if(xmlHttp.readyState==4)
                    if(xmlHttp.status==200){
                        if(requestType=="north")
                           listNorthStates();
                        else if(requestType=="all")
                           listAllStates();    
                    }
                       
            }
            function listNorthStates(){
                //alert('listNorthStates...');
                var xmlDoc=xmlHttp.responseXML;
                var northNode=xmlDoc.getElementsByTagName("north")[0];
                var out ="Northern States";
                var northStates=northNode.getElementsByTagName("state");
                outputList("Northern States",northStates);
            }
            function listAllStates(){
                //alert('listAllStates...');
                var xmlDoc=xmlHttp.responseXML;
                var allStates=xmlDoc.getElementsByTagName("state");
                outputList("All States in Document",allStates);
            }
            function outputList(title,states){
                var out = title ;
                var currentState=null;
                for(var i=0;i<states.length;i++){
                    currentState=states[i];
                    out=out +"\n-"+currentState.childNodes[0].nodeValue;
                }
                alert(out);
            }
        </script>
      

  3.   

    xmlHttp.onreadystatechange=handleStateChange(requsetType); 类型不匹配！！
      

  4.   

    因为你字母写错了 
    全局变量是
    requestType
    而在startRequest函数里写的是
    requsetType
    s和e 位置反了，所以在startRequest里面只改变一个局部变量而已