1.在IE低版本里，当用 get 请求发送数据时，会存在缓存问题：链接和上一次的一样，请求不会再发送给后台，而是用的缓存；假如后台更新，前端将无法呈现新内容，只能关闭浏览器。
解决方法：让请求地址不一样，但请求不变，比如加时间。
1 xhr.open("get","1.php?use=jj&pwd=123&_="+new Date().getTime(),true);完整封装
1.node.js环境
node server.js
1 var http = require("http"); 2 var server = http.createServer(function (req, res) { 3 ????if (req.url !== "/favicon.ico") { 4 ????????res.writeHead(200, {"Content-Type": "text/plain", "Access-Control-Allow-Origin": "http://localhost:63342"}); 5 ????????res.write("hello,我是从服务器端接收的") 6 ????} 7 ????res.end(); 8 }); 9 server.listen(8888, "localhost", function () {10 ????console.log("开始监听...");11 });2.html,js,css
1 <!DOCTYPE html> 2 <html> 3 <head> 4 ????<meta charset="utf-8"> 5 ????<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1"> 6 ????<title>ajax demo</title> 7 ????<meta name="description" content=""> 8 ????<meta name="keywords" content=""> 9 ????<link href="" rel="stylesheet">10 </head>11 <body>12 <div id="ajxT" style="width:100px;height:50px;background: pink;"></div>13 </body>14 <script>15 ????ajxT.onclick = function () {16 ????????ajax({17 ????????????type: "get",//可缺省，默认get18 ????????????url: "http://localhost:8888",19 ????????????aysn: true,//可缺省，默认true20 ????????????data: {//可缺省，扩展json[{},{},{}]21 ????????????????use: "afei",22 ????????????????pwd: 12345623 ????????????},24 ????????????success: function (i) {//可缺省25 ????????????????//var data=JSON.parse(i);//类数组的jsonstring->json，接着遍历json，在里面innerHTML,appendChild等等26 ????????????????var ajxT = document.getElementById(‘ajxT‘);27 ????????????????ajxT.innerHTML = i;28 29 ????????????},30 ????????????error: function (i) {//可缺省31 ????????????????alert(i);32 ????????????}33 ????????});34 ????};35 ????//ajax封装36 ????//参数说明:data:json 代表需要传递的数据，字符串自行拼接37 ????function ajax(json) {38 ????????var type = json.type || "GET",39 ????????????????url = json.url,40 ????????????????aysn = json.aysn !== false,41 ????????????????data = json.data,42 ????????????????success = json.success,43 ????????????????error = json.error;44 ????????//json->string,data存在才执行45 ????????data = data && (function () {46 ????????????????????var dataStr = "";47 ????????????????????for (var key in data) data += key + "=" + data[key] + "&";48 ????????????????????return dataStr;49 ????????????????})();50 ????????//让get请求的url后面跟上数据51 ????????if (/get/i.test(type)) {52 ????????????url += "?" + (data || "") + "_=" + new Date().getTime();//data存在就拼接data，不存在赋空53 ????????????//拼接时间解决get缓存问题，拼接时间放在此处，可避免缺省data时的缓存问题54 ????????????data = undefined;55 ????????}56 ????????var xhr = new XMLHttpRequest();57 ????????xhr.open(type, url, aysn);58 ????????xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");59 ????????xhr.send(data);60 ????????xhr.onreadystatechange = function () {61 ????????????if (xhr.readyState === 4) {62 ????????????????var status = this.status;63 ????????????????if (status >= 200 && status < 300) {64 ????????????????????success && success(this.responseText + new Date().getTime());65 ????????????????} else {66 ????????????????????error && error(status);67 ????????????????}68 ????????????}69 ????????}70 ????}71 </script>72 </html>ajax
原文地址：http://www.cnblogs.com/yuqlblog/p/7978035.html