Makes sure xhrs are actually aborted on unload in IE. Simplifies active xhrs...

Makes sure xhrs are actually aborted on unload in IE. Simplifies active xhrs caching in the process.

src/ajax/xhr.js

 (function( jQuery ) {
 
+var // #5280: next active xhr id and list of active xhrs' callbacks
+	xhrId = jQuery.now(),
+	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 {
@@ -13,18 +30,6 @@ function createActiveXHR() {
 	} catch( e ) {}
 }
 
-var // Next active xhr id
-	xhrId = jQuery.now(),
-
-	// active xhrs
-	xhrs = {},
-
-	// #5280: see below
-	xhrUnloadAbortInstalled,
-
-	// XHR used to determine supports properties
-	testXHR;
-
 // Create the request object
 // (This is still attached to ajaxSettings for backward compatibility)
 jQuery.ajaxSettings.xhr = window.ActiveXObject ?
@@ -62,23 +67,6 @@ if ( jQuery.support.ajax ) {
 			return {
 				send: function( headers, complete ) {
 
-					// #5280: we need to abort on unload or IE will keep connections alive
-					if ( !xhrUnloadAbortInstalled ) {
-
-						xhrUnloadAbortInstalled = 1;
-
-						jQuery(window).bind( "unload", function() {
-
-							// Abort all pending requests
-							jQuery.each( xhrs, function( _, xhr ) {
-								if ( xhr.onreadystatechange ) {
-									xhr.onreadystatechange( 1 );
-								}
-							} );
-
-						} );
-					}
-
 					// Get a new xhr
 					var xhr = s.xhr(),
 						handle,
@@ -142,7 +130,7 @@ if ( jQuery.support.ajax ) {
 								// Do not keep as active anymore
 								if ( handle ) {
 									xhr.onreadystatechange = jQuery.noop;
-									delete xhrs[ handle ];
+									delete xhrCallbacks[ handle ];
 								}
 
 								// If it's an abort
@@ -152,7 +140,6 @@ if ( jQuery.support.ajax ) {
 										xhr.abort();
 									}
 								} else {
-									// Get info
 									status = xhr.status;
 									responseHeaders = xhr.getAllResponseHeaders();
 									responses = {};
@@ -223,10 +210,15 @@ if ( jQuery.support.ajax ) {
 					if ( !s.async || xhr.readyState === 4 ) {
 						callback();
 					} else {
-						// Add to list of active xhrs
+						// Create the active xhrs callbacks list if needed
+						// and attach the unload handler
+						if ( !xhrCallbacks ) {
+							xhrCallbacks = {};
+							xhrOnUnloadAbort();
+						}
+						// Add to list of active xhrs callbacks
 						handle = xhrId++;
-						xhrs[ handle ] = xhr;
-						xhr.onreadystatechange = callback;
+						xhr.onreadystatechange = xhrCallbacks[ handle ] = callback;
 					}
 				},