Read file:// URLs in IE XMLHttpRequest
I'm developing a JavaScript application that's meant to be run either from a web server (over http) or from the file system (on a file:// URL).
As part of this code, I need to use XMLHttpRequest to load files in the same directory as the page and in subdirectories of the page.
This code works fine ("PASS") when executed on a web server, but doesn't work ("FAIL") in Internet Explorer 8 when run off the file system:
<html><head>
<script>
window.onload = function() {
var xhr = new XMLHttpRequest();
xhr.open("GET", window.location.href, false);
xhr.send(null);
if (/TestString/.test(xhr.responseText)) {
document.body.innerHTML="<p>PASS</p>";
}
}
</script>
<body><p>FAIL</p></body>
Of course, at first it fails because no scripts can run at all on the file system; the user is prompted a yellow bar, warning that "To help protect your security, Internet Explorer has restricted this webpage from running scripts or ActiveX controls that could access your computer."
But even once I click on the bar and "Allow Blocked Content" the page still fails; I get an "Access is Denied" error on the xhr.open call.
This puzzles me, because MSDN says that "For development purposes, the file:// protocol is allowed from the Local Machine zone." This local file should be part of the Local Machine Zone, right?
How can I get code like this to work? I'm fine with prompting the user with security warnings; I'm not OK with forcing them to turn off security in the control panel.
EDIT: I am not, in fact, loading an XML document in my case; I'm loading a plain text file (.txt).
Answer
Hmm, could it be the difference between the native XMLHttpRequest object and the ActiveX one? I seem to remember something about that. That is, instead of
var xhr = new XMLHttpRequest();
try
var xhr = new ActiveXObject("MSXML2.XMLHTTP");
Obviously, put some checks in place to see if the browser supports ActiveX. Of course, this is limited to IE only, as well.