Reduce duplication

modules/xmpp/JingleSessionPC.js

     this.removessrc = [];
 
     sdp.raw = sdp.session + sdp.media.join('');
-    this.peerconnection.setRemoteDescription(new RTCSessionDescription({type: 'offer', sdp: sdp.raw}),
+    /**
+     * Implements a failure callback which reports an error message and an
+     * optional error through (1) logger, (2) GlobalOnErrorHandler, and (3)
+     * queueCallback.
+     *
+     * @param {string} errmsg the error messsage to report
+     * @param {*} error an optional error to report in addition to errmsg
+     */
+    function reportError(errmsg, err) {
+        if (err) {
+           errmsg = errmsg + ': ' + err; // for logger and GlobalOnErrorHandler
+           logger.error(errmsg, err);
+        } else {
+           logger.error(errmsg);
+           err = errmsg; // for queueCallback
+        }
+        GlobalOnErrorHandler.callErrorHandler(new Error(errmsg));
+        queueCallback(err);
+    };
+    this.peerconnection.setRemoteDescription(
+        new RTCSessionDescription({type: 'offer', sdp: sdp.raw}),
         function() {
-
             if(self.signalingState == 'closed') {
-                var errmsg = "createAnswer attempt on closed state";
-                logger.error(errmsg);
-                GlobalOnErrorHandler.callErrorHandler(new Error(errmsg));
-                queueCallback(errmsg);
+                reportError("createAnswer attempt on closed state");
                 return;
             }
 
                     //modifiedAnswer.sdp = modifiedAnswer.sdp.replace(/a=setup:active/g, 'a=setup:actpass');
                     self.peerconnection.setLocalDescription(modifiedAnswer,
                         function() {
-                            if(successCallback){
-                                successCallback();
-                            }
+                            successCallback && successCallback();
                             queueCallback();
                         },
-                        function(error) {
-                            var errmsg = "modified setLocalDescription failed";
-                            GlobalOnErrorHandler.callErrorHandler(new Error(
-                                errmsg + ": " + error));
-                            logger.error(errmsg, error);
-                            queueCallback(error);
-                        }
+                        reportError.bind(
+                            undefined,
+                            "modified setLocalDescription failed")
                     );
                 },
-                function(error) {
-                    var errmsg = "modified answer failed";
-                    GlobalOnErrorHandler.callErrorHandler(new Error(
-                        errmsg + ": " + error));
-                    logger.error(errmsg, error);
-                    queueCallback(error);
-                }
+                reportError.bind(undefined, "modified answer failed")
             );
         },
-        function(error) {
-            var errmsg = 'modify failed';
-            GlobalOnErrorHandler.callErrorHandler(new Error(
-                errmsg + ": " + error));
-            logger.error(errmsg, error);
-            queueCallback(error);
-        }
+        reportError.bind(undefined, 'modify failed')
     );
 };
 

modules/xmpp/moderator.js

     });
 };
 
-Moderator.prototype.getLoginUrl =  function (urlCallback, failureCallback) {
+Moderator.prototype.getLoginUrl = function (urlCallback, failureCallback) {
+    this._getLoginUrl(/* popup */ false, urlCallback, failureCallback);
+};
+
+/**
+ *
+ * @param {boolean} popup false for {@link Moderator#getLoginUrl} or true for
+ * {@link Moderator#getPopupLoginUrl}
+ * @param urlCb
+ * @param failureCb
+ */
+Moderator.prototype._getLoginUrl = function (popup, urlCb, failureCb) {
     var iq = $iq({to: this.getFocusComponent(), type: 'get'});
-    iq.c('login-url', {
+    var attrs = {
         xmlns: 'http://jitsi.org/protocol/focus',
         room: this.roomName,
         'machine-uid': this.settings.getUserId()
-    });
+    };
+    var str = 'auth url'; // for logger
+    if (popup) {
+       attrs.popup = true;
+       str = 'POPUP ' + str;
+    }
+    iq.c('login-url', attrs);
+    /**
+     * Implements a failure callback which reports an error message and an error
+     * through (1) GlobalOnErrorHandler, (2) logger, and (3) failureCb.
+     *
+     * @param {string} errmsg the error messsage to report
+     * @param {*} error the error to report (in addition to errmsg)
+     */
+    function reportError(errmsg, err) {
+        GlobalOnErrorHandler.callErrorHandler(new Error(errmsg));
+        logger.error(errmsg, err);
+        failureCb(err);
+    }
     this.connection.sendIQ(
         iq,
         function (result) {
             var url = $(result).find('login-url').attr('url');
-            url = url = decodeURIComponent(url);
+            url = decodeURIComponent(url);
             if (url) {
-                logger.info("Got auth url: " + url);
-                urlCallback(url);
+                logger.info('Got ' + str + ': ' + url);
+                urlCb(url);
             } else {
-                var errmsg = "Failed to get auth url from the focus";
-                GlobalOnErrorHandler.callErrorHandler(new Error(errmsg));
-                logger.error(errmsg, result);
-                failureCallback(result);
+                reportError('Failed to get ' + str + ' from the focus', result);
             }
         },
-        function (error) {
-            var errmsg = "Get auth url error";
-            GlobalOnErrorHandler.callErrorHandler(new Error(errmsg));
-            logger.error(errmsg, error);
-            failureCallback(error);
-        }
+        reportError.bind(undefined, 'Get ' + str + ' error')
     );
 };
 
 Moderator.prototype.getPopupLoginUrl = function (urlCallback, failureCallback) {
-    var iq = $iq({to: this.getFocusComponent(), type: 'get'});
-    iq.c('login-url', {
-        xmlns: 'http://jitsi.org/protocol/focus',
-        room: this.roomName,
-        'machine-uid': this.settings.getUserId(),
-        popup: true
-    });
-    this.connection.sendIQ(
-        iq,
-        function (result) {
-            var url = $(result).find('login-url').attr('url');
-            url = url = decodeURIComponent(url);
-            if (url) {
-                logger.info("Got POPUP auth url:  " + url);
-                urlCallback(url);
-            } else {
-                var errmsg = "Failed to get POPUP auth url from the focus";
-                GlobalOnErrorHandler.callErrorHandler(new Error(errmsg));
-                logger.error(errmsg, result);
-                failureCallback(result);
-            }
-        },
-        function (error) {
-            var errmsg = "Get POPUP auth url error";
-            GlobalOnErrorHandler.callErrorHandler(new Error(errmsg));
-            logger.error(errmsg, error);
-            failureCallback(error);
-        }
-    );
+    this._getLoginUrl(/* popup */ true, urlCallback, failureCallback);
 };
 
 Moderator.prototype.logout =  function (callback) {