XMLHttpRequest使用详解
本文详细介绍了一个使用XMLHttpRequest进行网络请求的JavaScript类net.ContentLoader。该类通过GET方式加载指定URL的内容，并提供了回调函数来处理加载完成及错误情况。文章还展示了如何根据不同状态码处理响应。
1
var net=new Object();
2net.READY_STATE_UNINITIALIZED=0;
3net.READY_STATE_LOADING=1;
4net.READY_STATE_LOADED=2;
5net.READY_STATE_INTERACTIVE=3;
6net.READY_STATE_COMPLETE=4;
7
net.ContentLoader=function(url,onload,onerror)
{
8
this.url=url;
9this.req=null;
10this.onload=onload;
11this.onerror=(onerror) ? onerror : this.defaultError;
12this.loadXMLDoc(url);
13
}
14net.ContentLoader.prototype={
15
loadXMLDoc:function(url){
16if (window.XMLHttpRequest){
17this.req=new XMLHttpRequest();
18} else if (window.ActiveXObject){
19this.req=new ActiveXObject("Microsoft.XMLHTTP");
20
}
21if (this.req){
22try{
23var loader=this;
24this.req.onreadystatechange=function(){
25loader.onReadyState.call(loader);
26}
27this.req.open('GET',url,true);
28this.req.send(null);
29}catch (err){
30this.onerror.call(this);
31}
32}
33},
34onReadyState:function(){
35var req=this.req;
36var ready=req.readyState;
37if (ready==net.READY_STATE_COMPLETE){
38var httpStatus=req.status;
39if (httpStatus==200 || httpStatus==0){
40this.onload.call(this);
41}else{
42this.onerror.call(this);
43}
44}
45},
46defaultError:function(){
47alert("error fetching data!"
48+"\n\nreadyState:"+this.req.readyState
49+"\nstatus: "+this.req.status
50+"\nheaders: "+this.req.getAllResponseHeaders());
51}
52}
var net=new Object();2
net.READY_STATE_UNINITIALIZED=0;3
net.READY_STATE_LOADING=1;4
net.READY_STATE_LOADED=2;5
net.READY_STATE_INTERACTIVE=3;6
net.READY_STATE_COMPLETE=4;7
net.ContentLoader=function(url,onload,onerror){8
this.url=url;9
this.req=null;10
this.onload=onload;11
this.onerror=(onerror) ? onerror : this.defaultError;12
this.loadXMLDoc(url);13
}14
net.ContentLoader.prototype={15
loadXMLDoc:function(url){16
if (window.XMLHttpRequest){17
this.req=new XMLHttpRequest();18
} else if (window.ActiveXObject){19
this.req=new ActiveXObject("Microsoft.XMLHTTP");20
}21
if (this.req){22
try{23
var loader=this;24
this.req.onreadystatechange=function(){25
loader.onReadyState.call(loader);26
}27
this.req.open('GET',url,true);28
this.req.send(null);29
}catch (err){30
this.onerror.call(this);31
}32
}33
},34
onReadyState:function(){35
var req=this.req;36
var ready=req.readyState;37
if (ready==net.READY_STATE_COMPLETE){38
var httpStatus=req.status;39
if (httpStatus==200 || httpStatus==0){40
this.onload.call(this);41
}else{42
this.onerror.call(this);43
}44
}45
},46
defaultError:function(){47
alert("error fetching data!"48
+"\n\nreadyState:"+this.req.readyState49
+"\nstatus: "+this.req.status50
+"\nheaders: "+this.req.getAllResponseHeaders());51
}52
}
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