it is impossible to cancel JSONP polling request - comprehend that

Author: majek

lib/trans-jsonp-polling.js

@@ -68,16 +68,36 @@ JsonPTransport.prototype.doCleanup = function() {
 var jsonPReceiverWrapper = function(url, constructReceiver, user_callback) {
     var id = 'a' + utils.random_string(6);
     var url_id = url + '?c=' + escape(WPrefix + '.' + id);
+
+    // Unfortunately it is not possible to abort loading of the
+    // script. We need to keep track of frake close frames.
+    var aborting = 0;
+
     // Callback will be called exactly once.
     var callback = function(frame) {
-        delete _window[WPrefix][id];
-        user_callback(frame);
+        switch(aborting) {
+        case 0:
+            // Normal behaviour - delete hook _and_ emit message.
+            delete _window[WPrefix][id];
+            user_callback(frame);
+            break;
+        case 1:
+            // Fake close frame - emit but don't delete hook.
+            user_callback(frame);
+            aborting = 2;
+            break;
+        case 2:
+            // Got frame after connection was closed, delete hook, don't emit.
+            delete _window[WPrefix][id];
+            break;
+        }
     };
 
     var close_script = constructReceiver(url_id, callback);
     _window[WPrefix][id] = close_script;
     var stop = function() {
         if (_window[WPrefix][id]) {
+            aborting = 1;
             _window[WPrefix][id](utils.closeFrame(1000, "JSONP user aborted read"));
         }
     };

lib/trans-jsonp-receiver.js

@@ -21,6 +21,8 @@ var jsonPGenericReceiver = function(url, callback) {
         }
         if (script) {
             clearTimeout(tref);
+            // Unfortunately, you can't really abort script loading of
+            // the script.
             script.parentNode.removeChild(script);
             script.onreadystatechange = script.onerror =
                 script.onload = script.onclick = null;