没有为IE 7,8＆amp; 9

Question

我在理解Jquery代码时遇到了问题。我正在尝试启用应用程序（Backbone）在IE 7,8＆amp; 9.问题在于Jquery（版本1.10.2）Ajax准备：

  function createStandardXHR() {

    debugger;
    try {
        return new window.XMLHttpRequest();
    } catch( e ) {}
}

function createActiveXHR() {
    try {
        return new window.ActiveXObject("Microsoft.XMLHTTP");
    } catch( e ) {}
}

// Create the request object
// (This is still attached to ajaxSettings for backward compatibility)
jQuery.ajaxSettings.xhr = window.ActiveXObject ?
    /* Microsoft failed to properly
     * implement the XMLHttpRequest in IE7 (can't request local files),
     * so we use the ActiveXObject when it is available
     * Additionally XMLHttpRequest can be disabled in IE7/IE8 so
     * we need a fallback.
     */
    function() {
        return !this.isLocal && createStandardXHR() || createActiveXHR();
    } :
    // For all other browsers, use the standard XMLHttpRequest object
    createStandardXHR;

// Determine support properties
xhrSupported = jQuery.ajaxSettings.xhr();
jQuery.support.cors = !!xhrSupported && ( "withCredentials" in xhrSupported );
xhrSupported = jQuery.support.ajax = !!xhrSupported;

更确切地说：

jQuery.support.cors = !!xhrSupported && ( "withCredentials" in xhrSupported );

在IE 7,8＆amp; 9给出False并阻止我的申请继续进行。我可以自己检测特定的IE版本，但Jquery应该自动执行此操作...或者我失败了什么？