Ajax中的高级请求和响应

1. 在回调函数中处理服务器的响应

    在代码中加入:alert("status is " + request.status);

 2. 获取 0 就绪状态 

 function getSalesData() {
     // Create a request object
     createRequest();		
     alert("Ready state is: " + request.readyState);
     // Setup (initialize) the request
     var url = "/boards/servlet/UpdateBoardSales";
     request.open("GET", url, true);
     request.onreadystatechange = updatePage;
     request.send(null);
   }

3. 使用服务器上返回的响应

function updatePage() {
    if (xmlhttp.readyState==4 && xmlhttp.status==200) 

       { 

          document.getElementById("txtHint").innerHTML=xmlhttp.responseText;

        }     

      }

4.检查有效状态代码

function updatePage() {
     if (request.readyState == 4) {
       if (request.status == 200) {
         var response = request.responseText.split("|");
         document.getElementById("order").value = response[0];
         document.getElementById("address").innerHTML =
           response[1].replace(/\n/g, "<br />");
       } else if (request.status == 404) {
         alert ("Requested URL is not found.");
       } else if (request.status == 403) {
         alert("Access denied.");
       } else
         alert("status is " + request.status);
     }
   }

5. 检查某个 URL 是否存在

   function updatePage() {
     if (request.readyState == 4) {
       if (request.status == 200) {
         alert("URL exists");
       } else if (request.status == 404) {
         alert("URL does not exist.");
       } else {
         alert("Status is: " + request.status);
       }
     }
   }