一个比较方便通用的自定义Ajax函数

function Ajax()   
{   
var len=arguments.length;   
var type,url,postdata,fn;   
if(len<2)   
{   
alert('没有2个一下参数的重载,至少必须指定请求类型(type)和url地址!');   
return;   
}   
type=arguments[0];   
url=arguments[1];   
if(len>2)   
{   
var args=arguments[2];   
if(typeof(args)=="string")   
{   
postdata=args;   
}   
}   
var xhr = window.ActiveXObject ? new ActiveXObject("Microsoft.XMLHTTP") : new XMLHttpRequest();   
xhr.open(type,url,true);   
xhr.setRequestHeader("Content-Type","application/x-www-form-urlencoded");   
fn = arguments[len-1];   
xhr.onreadystatechange = function (){   
if(xhr.readyState==4)   
{   
if(xhr.status==200)   
{   
if(typeof(fn)=="function")   
fn(xhr.responseText);   
}   
else  
{   
alert("你所请求的页面有异常");   
}   
}   
};   
xhr.send(postdata);   
}   

function Test()   
{   
Ajax("get","/WebRoot/servlet/TestAjax");   
Ajax("get","/WebRoot/servlet/TestAjax",function (date){   
alert("Get Date:n"+date);   
});   
Ajax("post","/WebRoot/servlet/TestAjax");   
Ajax("post","/WebRoot/servlet/TestAjax",function (date){   
alert("Post Date:n"+date);   
});   
Ajax("post","/WebRoot/servlet/TestAjax","username=jonllen&pwd=123456",function (date){   
alert("Post Date:n"+date);   
});   
}  
function Ajax()
{
var len=arguments.length;
var type,url,postdata,fn;
if(len<2)
{
alert('没有2个一下参数的重载,至少必须指定请求类型(type)和url地址!');
return;
}
type=arguments[0];
url=arguments[1];
if(len>2)
{
var args=arguments[2];
if(typeof(args)=="string")
{
postdata=args;
}
}
var xhr = window.ActiveXObject ? new ActiveXObject("Microsoft.XMLHTTP") : new XMLHttpRequest();
xhr.open(type,url,true);
xhr.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
fn = arguments[len-1];
xhr.onreadystatechange = function (){
if(xhr.readyState==4)
{
if(xhr.status==200)
{
if(typeof(fn)=="function")
fn(xhr.responseText);
}
else
{
alert("你所请求的页面有异常");
}
}
};
xhr.send(postdata);
}
function Test()
{
Ajax("get","/WebRoot/servlet/TestAjax");
Ajax("get","/WebRoot/servlet/TestAjax",function (date){
alert("Get Date:n"+date);
});
Ajax("post","/WebRoot/servlet/TestAjax");
Ajax("post","/WebRoot/servlet/TestAjax",function (date){
alert("Post Date:n"+date);
});
Ajax("post","/WebRoot/servlet/TestAjax","username=jonllen&pwd=123456",function (date){
alert("Post Date:n"+date);
});
}