javascript ajax

javascript实现的ajax主要代码如下：

var xmlHttp = false; 
function ajaxScore(_ajaxCon){
//ajax处理评分
var callBackResult ;
var _assetid = $('resource_id').innerHTML;
if (window.XMLHttpRequest) {// code for IE7+, Firefox, Chrome, Opera, Safari
xmlHttp = new XMLHttpRequest();
}
else {// code for IE6, IE5
xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
}
xmlHttp.setRequestHeader( "Connection", "close");
var url="http://172.30.93.204:8078/gateway/assetScoreServlet?assetid="+_assetid+"&stbId=''&score="+_ajaxCon;
//var url = "";//获取播放地址url
if (url) {
xmlHttp.onreadystatechange = function(){
if (xmlHttp.readyState == 4 ) {
if(xmlHttp.status == 200){
if(curTimeoutErrorInfo > 0)
clearTimeout(curTimeoutErrorInfo) ;
callBackResult = xmlHttp.responseText;//xmlHttp.responseText is callback value
//$("film").innerHTML = callBackResult ;
if(eval(callBackResult)[0].url == 'ok'){
$("resultError").innerHTML = "评分成功！";
$("error").style.visibility = "visible";
setTimeout(function(){$("error").style.visibility = "hidden";},2000);
}
}
}
else{//network not success
if(curTimeoutErrorInfo > 0)
clearTimeout(curTimeoutErrorInfo) ;
curTimeoutErrorInfo = setTimeout(function(){
$("resultError").innerHTML = "评分失败，请检查网络连接！";
$("error").style.visibility = "visible";
setTimeout(function(){$("error").style.visibility = "hidden";},2000);

},2000) ;
}
}
xmlHttp.open("POST", url, true);
xmlHttp.send();
}
else {
//$("play_num_" + line).innerHTML = "";//URL not exist
}
//alert(_ajaxCon); 
}

　　下面也是一个简单的ajax写法：

var TSTimeSpan = 0;
var requests = new Array();
function ajax_create_request(context)
{
 var pos = requests.length;
        
        if (pos < 10)   //???
        {
            for (var i = 0; i < pos; i++)
            {
                if (requests[i].readyState == 4)
                {
                    requests[i].abort();
                    requests[i].context = context;
                    return requests[i];
                }
            }
        }
        else
        {
            for (var i = 0; i < pos; i++)
            {
                if (requests[i].readyState == 4)
                {
                    requests[i].abort();
                }
                requests[i].obj = null;
                requests[i]=null;
            }
            requests = new Array();
            pos = 0;
        }
  
        requests[pos] = Object();
        requests[pos].obj = XMLHttpRequest();
 requests[pos].context = context;
        return requests[pos];
}
function ajax_request(userid, action, clientID, lastState, url, data, callback, httpresponse, context, objname)
{
 var request = ajax_create_request(context);
 request.obj.onreadystatechange = function()
 {
  if (request.obj)
  {
      if(request.obj.readyState == 4)
      {
       httpresponse(new ajax_response(request));
       if (callback)
       {
           callback(new ajax_response(request));
       }
   }
  }
 }
 
 request.obj.open('GET', url, true);
 request.obj.setRequestHeader( "Accept", "text/xml");
 request.obj.setRequestHeader("Content-Type", "text/xml");
        request.obj.setRequestHeader("charset", "utf-8");
 request.obj.setRequestHeader( "User-id", userid);//设置header
 request.obj.setRequestHeader( "User-action", action);
 request.obj.setRequestHeader( "TS-ClientID", clientID);
    request.obj.setRequestHeader( "X-Last-State", lastState);
    request.obj.setRequestHeader( "User-Json", data);
    request.obj.setRequestHeader( "Obj-Name", objname);
    request.obj.setRequestHeader( "S-Time", "");
    request.obj.setRequestHeader( "TS-SpanTime", TSTimeSpan);
 request.obj.send(null);
}

function ajax_response(request)
{
 this.request = request.obj;
 this.value = null;
 this.lastState = null;
 this.status = request.obj.status;
 this.context = request.context;
 this.value = this.request.responseText;
 this.clientid = this.request.getResponseHeader( "TS-ClientID");
 this.sTime = this.request.getResponseHeader( "S-Time" );//获取header
 this.objName = this.request.getResponseHeader( "Obj-Name" );
    TSTimeSpan = this.request.getResponseHeader( "TS-SpanTime" ); 
 return this;
}