AJAX入门札记

学习笔记

例子：

??? var http_request = false;

??? function send_request(url,method) {//初始化指定处理函数、发送请求的函数

?????? http_request = false;

?????? //开始初始化XMLHttpRequest对象

?????? if(window.XMLHttpRequest) { //Mozilla 浏览器

?????????? http_request = new XMLHttpRequest();

?????????? if (http_request.overrideMimeType) {//设置MiME类别

????????????? http_request.overrideMimeType('text/xml');

?????????? }

?????? }

?????? else if (window.ActiveXObject) { // IE浏览器

?????????? try {

????????????? http_request = new ActiveXObject("Msxml2.XMLHTTP");

?????????? } catch (e) {

????????????? try {

????????????????? http_request =new ActiveXObject("Microsoft.XMLHTTP");

????????????? } catch (e) {}

?????????? }

?????? }

?????? if (!http_request) { // 异常，创建对象实例失败

?????????? window.alert("不能创建XMLHttpRequest对象实例.");

?????????? return false;

?????? }

?????? http_request.onreadystatechange = method;//method是事件处理函数

?????? // 确定发送请求的方式和URL以及是否同步执行下段代码

?????? http_request.open("GET", url, true);//创建一个Http请求

?????? http_request.send(null);//提交一个http请求

??? }

??? function 函数名() {?????? //创建一个事件处理函数

??????? if (http_request.readyState == 4) { // 判断对象状态

?????????? ????? if (http_request.status == 200) { // 信息已经成功返回，开始处理信息

??????????? ???????? document.getElementById('d').style.display='block'?'block':'none';

?????????? ???????? var res = http_request.responseText;

?????????? ???????? res=eval('(' + res + ')');

?????????? ???????? //向jsp页面添加处理信息

???????? ??????? } else { //页面不正常

??????????????? ????? alert("您所请求的页面有异常。");

??????????? ???? }

??????? }

??? }

1、根据不同浏览器创建一个XMLHttpRequest对象

?????? if(window.XMLHttpRequest) { //Mozilla 浏览器

?????????? http_request = new XMLHttpRequest();

?????????? if (http_request.overrideMimeType) {//设置MiME类别

????????????? http_request.overrideMimeType('text/xml');

?????????? }

?????? }

?????? else if (window.ActiveXObject) { // IE浏览器

?????????? try {

????????????? http_request = new ActiveXObject("Msxml2.XMLHTTP");

?????????? } catch (e) {

????????????? try {

????????????????? http_request = new ActiveXObject("Microsoft.XMLHTTP");

????????????? } catch (e) {}

?????????? }

?????? }??

2、指定一个事件处理函数

??? //http_request.onreadystatechange = method;//method是事件处理函数

??? 创建一个事件处理函数判断当前状态，执行操作：

??? if (http_request.readyState == 4) { // 判断对象状态

????????? 　　if (http_request.status == 200) { // 信息已经成功返回，开始处理信息

????????????? 　　var res=http_request.responseText;//json数据

?????? ? ????? ?res=eval('('+res+')');

????????? 　　} else { //页面不正常

????????????? 　　alert("您所请求的页面有异常。");

????????? 　　}

????? 　　}

3、创建一个Http请求

??? http_request.open("GET", url, true);

4、提交一个Http请求

??? http_request.send(null);