利用javascript实现原生简单ajax的方法。

利用javascript实现原生简单ajax的方法。 

实现ajax之前必须要创建一个 XMLHttpRequest （IE6↑）对象。如果不支持创建该对象的浏览器，则需要创建 ActiveXObject（IE6），具体方法如下： 

var objectRequest; 
function createXmlHttpRequest() { 
if (window.XMLHttpRequest) { 
objectRequest=new XMLHttpRequest(); 
} else if (window.ActiveXObject ) 
objectRequest= new ActiveXObject("Microsoft.XMLHTTP"); 
} 

（1）实现简单的ajax get请求： 

function doGet(url){ 
createxmlHttpRequest(); 
objectRequest.open("GET",url,true); 
objectRequest.send(null); 
objectRequest.onreadystatechange = function() { 
if ((objectRequest.readyState == 4) && (objectRequest.status == 200)) { 
//TODO请求成功回调代码
} else { 
//TODO请求失败回调代码
} 
} 
} 

（2）实现简单的ajax post请求： 

function doPost(url,data){ 
createxmlHttpRequest(); 
objectRequest.open("POST",url,true); 
objectRequest.setRequestHeader("Content-Type","application/x-www-form-urlencoded"); 
objectRequest.send(data); 
objectRequest.onreadystatechange = function() { 
if ((objectRequest.readyState == 4) && (objectRequest.status == 200)) { 
//TODO请求成功回调代码
} else { 
//TODO请求失败回调代码
} 
} 
}