+ xhrCallbacks,
+
+ // XHR used to determine supports properties
+ testXHR;
+
+// #5280: Internet Explorer will keep connections alive if we don't abort on unload
+function xhrOnUnloadAbort() {
+ jQuery( window ).unload(function() {
+ // Abort all pending requests
+ for ( var key in xhrCallbacks ) {
+ xhrCallbacks[ key ]( 0, 1 );
+ }
+ });
+}
+
+// Functions to create xhrs
+function createStandardXHR() {
+ 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;
+
+// Test if we can create an xhr object
+testXHR = jQuery.ajaxSettings.xhr();
+jQuery.support.ajax = !!testXHR;
+
+// Does this browser support crossDomain XHR requests
+jQuery.support.cors = testXHR && ( "withCredentials" in testXHR );
+
+// No need for the temporary xhr anymore
+testXHR = undefined;
+
+// Create transport if the browser can provide an xhr
+if ( jQuery.support.ajax ) {
+
+ jQuery.ajaxTransport(function( s ) {
+ // Cross domain only allowed if supported through XMLHttpRequest
+ if ( !s.crossDomain || jQuery.support.cors ) {
+
+ var callback;
+
+ return {
+ send: function( headers, complete ) {
+
+ // Get a new xhr
+ var xhr = s.xhr(),
+ handle,
+ i;
+
+ // Open the socket
+ // Passing null username, generates a login popup on Opera (#2865)
+ if ( s.username ) {
+ xhr.open( s.type, s.url, s.async, s.username, s.password );
+ } else {
+ xhr.open( s.type, s.url, s.async );
+ }