Ajax---001

创建xmlhttp对象

 1 function ajaxFunction(){
 2             var xmlHttp;
 3             try {
 4                 //firefox,opera,safari
 5                 xmlHttp = new XMLHttpRequest();
 6             } catch (e) {
 7                 try {
 8                     //Internet explore
 9                     xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
10                 } catch (e) {
11                     try {
12                         xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
13                     } catch (e) {
14                     }
15 
16                 }
17             }
18             return xmlHttp;
19         }

使用GET或POST方式不带参数时的访问方式

1 function func02(){
2             var request = ajaxFunction();
3             request.open("GET","servletURL",true);
4             //request.open("POST","servletURL",true);
5             request.send();
6         }

使用POST方式带数据的访问方式

 1 function func01(){
 2             //创建ajax对象
 3             var myrequest = ajaxFunction();
 4 
 5             //发送请求
 6             myrequest.open("POST","DemoServlet01",true);
 7             myrequest.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
 8             myrequest.onreadystatechange = function(){
 9                 if(myrequest.readyState == 4 && myrequest.status == 200){
10                     alert(myrequest.responseText);
11                 }
12 
13             }
14             myrequest.send("name=aliy&age=19");
15         }

使用GET方式请求时可能得到的是缓存的结果，可以通过向url中添加唯一的uid来解决

1 xmlhttp.open("GET","demo_get.asp?t=" + Math.random(),true);
2 xmlhttp.send();