XMLHttpRequest status 0 (responseText is empty)
Cannot get data with XMLHttpRequest (status 0 and responseText is empty):
xmlhttp=new XMLHttpRequest();
xmlhttp.open("GET","http://www.w3schools.com/XML/cd_catalog.xml", true);
xmlhttp.onreadystatechange=function()
{
if(xmlhttp.readyState==4)
alert("status " + xmlhttp.status);
}
xmlhttp.send();
It alerts "status 0".
The same situation with the localhost request (cd_catalog.xml is saved as a local file)
xmlhttp.open("GET","http://localhost/cd_catalog.xml", true);
But with the localhost IP request
xmlhttp.open("GET","http://127.0.0.1/cd_catalog.xml", true);
and with the local file request
xmlhttp.open("GET","cd_catalog.xml", true);
everything is OK (status 200)
What can cause the problem (status=0) with the online request?
PS: Live HTTP Headers shows that everything is OK in all 4 cases:
HTTP/1.1 200 OK Content-Length: 4742
PS2: Apache local web server on VMWare (host OS Win7, Guest OS Ubuntu, Network adapter – NAT). Browser – Firefox.
状态为0，当你的HTML文件包含脚本在浏览器中通过文件协议打开时。请务必将文件放在你的服务器（apache或tomcat）中，然后在浏览器中通过http协议打开它（例如http： //localhost/myfile.html）这是解决方案。
其实确保你的按钮类型是按钮不提交，导致我最近遇到的状态冲突。
The cause of your problems is that you are trying to do a cross-domain call and it fails .
If you're doing localhost development you can make cross-domain calls - I do it all the time.
For Firefox, you have to enable it in your config settings
signed.applets.codebase_principal_support = true
Then add something like this to your XHR open code:
if (isLocalHost()){
if (typeof(netscape) != 'undefined' && typeof(netscape.security) != 'undefined'){
netscape.security.PrivilegeManager.enablePrivilege('UniversalBrowserRead');
}
}
For IE, if I remember right, all you have to do is enable the browser's Security setting under "Miscellaneous → Access data sources across domains" to get it to work with ActiveX XHRs.
IE8 and above also added cross-domain capabilities to the native XmlHttpRequest objects, but I haven't played with those yet.
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