JQuery 1.4.2 + IE + $.ajax

[scottchiefbaker]

I have created a test case for a reproducible $.ajax bug with IE and JQuery 1.4.2. See the test case below for more information. I have confirmed this bug is present in IE7 and IE8.

​http://www.perturb.org/tmp/ie-ajax.html

[Bradley]

Verified in IE7 (did not test IE8).

The problem seems to be related to a change in behavior with respect to the xhr method used in IE. Previously, the ActiveX Object was used whenever possible. In 1.4, the behavior is to use XMLHttpRequest except for local files.

jQuery 1.3:

xhr:function(){
    return window.ActiveXObject ? new ActiveXObject("Microsoft.XMLHTTP") : new XMLHttpRequest();
}

jQuery 1.4.2:

xhr: window.XMLHttpRequest && (window.location.protocol !== "file:" || !window.ActiveXObject) ?
    function() {
        return new window.XMLHttpRequest();
    } :
    function() {
        try {
            return new window.ActiveXObject("Microsoft.XMLHTTP");
        } catch(e) {}
    }

By passing a function with the old behavior to the ajax setting "xhr", we can effectively force the old behavior and the problem goes away:

$.ajax({
    url: 'ajax.html',
    xhr: function() { return new window.ActiveXObject("Microsoft.XMLHTTP"); },
    success: ...
});

[scottchiefbaker]

Test case

[Bradley]

Duplicate of #6480

[Bradley]

Duplicate of #6298.