Revert "Ajax: remove "onunload" event handler"

This reverts commit 4632e55870a00a70e737a862cdb0820278cec0fe.

diff --git a/src/ajax/xhr.js b/src/ajax/xhr.js
index 6502d24c26ffdc9a61b164a21913a6491e20aff7..7e41409715061fd8ec47fb6d67bc855ad649a301 100644 (file)
--- a/src/ajax/xhr.js
+++ b/src/ajax/xhr.js
@@ -40,7 +40,20 @@ jQuery.ajaxSettings.xhr = window.ActiveXObject !== undefined ?
        // For all other browsers, use the standard XMLHttpRequest object
        createStandardXHR;
 
-var xhrSupported = jQuery.ajaxSettings.xhr();
+var xhrId = 0,
+       xhrCallbacks = {},
+       xhrSupported = jQuery.ajaxSettings.xhr();
+
+// Support: IE<10
+// Open requests must be manually aborted on unload (#5280)
+// See https://support.microsoft.com/kb/2856746 for more info
+if ( window.attachEvent ) {
+       window.attachEvent( "onunload", function() {
+               for ( var key in xhrCallbacks ) {
+                       xhrCallbacks[ key ]( undefined, true );
+               }
+       } );
+}
 
 // Determine support properties
 support.cors = !!xhrSupported && ( "withCredentials" in xhrSupported );
@@ -59,7 +72,8 @@ if ( xhrSupported ) {
                        return {
                                send: function( headers, complete ) {
                                        var i,
-                                               xhr = options.xhr();
+                                               xhr = options.xhr(),
+                                               id = ++xhrId;
 
                                        // Open the socket
                                        xhr.open(
@@ -105,6 +119,11 @@ if ( xhrSupported ) {
                                                }
                                        }
 
+                                       // Do send the request
+                                       // This may raise an exception which is actually
+                                       // handled in jQuery.ajax (so no try/catch here)
+                                       xhr.send( ( options.hasContent && options.data ) || null );
+
                                        // Listener
                                        callback = function( _, isAbort ) {
                                                var status, statusText, responses;
@@ -113,6 +132,7 @@ if ( xhrSupported ) {
                                                if ( callback && ( isAbort || xhr.readyState === 4 ) ) {
 
                                                        // Clean up
+                                                       delete xhrCallbacks[ id ];
                                                        callback = undefined;
                                                        xhr.onreadystatechange = jQuery.noop;
 
@@ -168,8 +188,6 @@ if ( xhrSupported ) {
                                        // handled in jQuery.ajax (so no try/catch here)
                                        if ( !options.async ) {
 
-                                               xhr.send( ( options.hasContent && options.data ) || null );
-
                                                // If we're in sync mode we fire the callback
                                                callback();
                                        } else if ( xhr.readyState === 4 ) {
@@ -180,13 +198,8 @@ if ( xhrSupported ) {
                                        } else {
 
                                                // Register the callback, but delay it in case `xhr.send` throws
-                                               xhr.onreadystatechange = function() {
-                                                       if ( callback ) {
-                                                               window.setTimeout( callback );
-                                                       }
-                                               };
-
-                                               xhr.send( ( options.hasContent && options.data ) || null );
+                                               // Add to the list of active xhr callbacks
+                                               xhr.onreadystatechange = xhrCallbacks[ id ] = callback;
                                        }
                                },