使用JavaScript的XMLHttpRequest发送请求

使用XMLHttpRequest对象分为4部完成:

 

1.创建XMLHttpRequest组建

 

2.设置回调函数

 

3.初始化XMLHttpRequest组建

 

4.发送请求

 

实例代码：

 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！");}}}