<!DOCTYPE html><html><head><title>ajax</title><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><script language="javascript" type="text/javascript">//通过这个函数来异步获取信息function Ajax() {var xmlHttpReq = null; //声明一个空对象用来装入XMLHttpRequestif(window.ActiveXObject) { //IE5 IE6是以ActiveXObject的方式引入XMLHttpRequestxmlHttpReq = new ActiveXObject("Microsoft.XMLHTTP");} else if(window.XMLHttpRequest) {xmlHttpReq = new XMLHttpRequest();}if(xmlHttpReq != null) { //如果对象实例化成功 xmlHttpReq.open("GET", "example.txt", true); //调用open()方法并采用异步方式xmlHttpReq.onreadystatechange = RequestCallBack; //设置回调函数xmlHttpReq.send(null);}function RequestCallBack() {if(xmlHttpReq.readyState == 4 && xmlHttpReq.status == 200) {document.getElementById("resText").innerHTML = xmlHttpReq.responseText;}}}</script></head><body>1.创建xhr对象，并实例化2.设置回调函数（判断readyState和status的值；写入值）在open之前3.调用open()方法4.调用send()方法<h3>查看留言：</h3><input type="button" value="Ajax提交" onclick="Ajax();" /><div id="resText"></div></body></html>
ajax
原文地址：http://www.cnblogs.com/zyxie154/p/7440592.html