JSP中使用AJAX验证用户是否存在

<script type="text/javascript">var xmlHttpReq;//创建XMLHTTP对象     function createXMLHttpRequest() {if (window.ActiveXObject) {xmlHttpReq = new ActiveXObject("MSXML2.XMLHTTP.3.0");} else {xmlHttpReq = new XMLHttpRequest();}}//检查用户     function checkUser() {createXMLHttpRequest();var userName = document.getElementById("username").value;var passWord = document.getElementById("password").value;//处理检查的地址     var url = "testUserIsExist.jsp?username=" + userName + "&"+ "password=" + passWord;xmlHttpReq.open("POST", url, true);xmlHttpReq.onreadystatechange = showResult;//showResult是当onreadystatechange的值改变时触发的javascript函数     xmlHttpReq.send();}function showResult() {if (xmlHttpReq.readyState == 4) {if (xmlHttpReq.status == 200) {var result = xmlHttpReq.responseText;//将响应信息作为字符串返回var checkResult = document.getElementById("msg").innerHTML = result;}}} </script>

其中

document.getElementById("msg")

为一个标签，设置其值为返回的结果