Ajax无刷新数据更新

<script type="text/javascript">

//异步请求对象
var xmlRequest;

//得到请求对象 
function getXMLHttpRequestObject() {

//不同的浏览器创建方式不同
try {
xmlRequest = new XMLHttpRequest(); //Firefox ,safari
} catch (e) {
//IE
try {
xmlRequest = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
xmlRequest = new ActiveXObject("Microsoft.XMLHTTP");
}
}
return xmlRequest;//返回
}
//检查用户是否存在
function checkType(selectType) {
alert(selectType);
//用户名输入不能为空
if (selectType == "") {
document.getElementById("selectType").innerHTML = "<font color='red'>&nbsp;不能为空！</font>";
return;
}
//得到请求对象
xmlRequest = getXMLHttpRequestObject();
if (xmlRequest == null) {
alert("您的浏览器不支持AJAX!");
return;
}
var url = "/datacenter/analysisBLOAction.action"; //请求页面
url += "?selectType=" + selectType; //用户名
url = encodeURI(url);
url = encodeURI(url);
xmlRequest.onreadystatechange = stateChanged;//状态改变调用函数
xmlRequest.open("POST", url, true);
//xmlRequest.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded; charset=UTF-8');
xmlRequest.send(null); // 发送请求
}
//是否已经存在检查
function stateChanged() {
if (xmlRequest.readyState == 4) {
if (xmlRequest.status == 200) {
showMess();
} else {
//页面不正常
window.alert("您所请求的页面有异常。");
}
} else {
//请求状态还没有成功，页面等待
document.getElementById("selectType").innerHTML = "检查中...";
}
}
//检查 异步处理显示信息
function showMess() {
var message = xmlRequest.responseText;
document.getElementById("selectType").innerHTML = message;
}
</script>