使用JavaScript的XMLHttpRequest发送请求

var userName;
var passWord;
var xmlHttpRequest;

//XmlHttpRequest对象
function createXmlHttpRequest(){
if(window.ActiveXObject){ //如果是IE浏览器
return new ActiveXObject("Microsoft.XMLHTTP");
}else if(window.XMLHttpRequest){ //非IE浏览器
return new XMLHttpRequest();
}
}

function onLogin(){
userName = document.f1.username.value;
passWord = document.f1.password.value;

var url = "LoginServlet?username="+userName+"&password="+passWord+"";

//1.创建XMLHttpRequest组建
xmlHttpRequest = createXmlHttpRequest();

//2.设置回调函数
xmlHttpRequest.onreadystatechange = zswFun;

//3.初始化XMLHttpRequest组建
xmlHttpRequest.open("POST",url,true);

//4.发送请求
xmlHttpRequest.send(null);
}

//回调函数
function zswFun(){
if(xmlHttpRequest.readyState == 4 && xmlHttpRequest.status == 200){
var b = xmlHttpRequest.responseText;
if(b == "true"){
alert("登录成功！");
}else{
alert("登录失败！");
}
}
}