better practices

Author: odeimaiz

services/static-webserver/client/source/class/osparc/Application.js

@@ -506,11 +506,13 @@ qx.Class.define("osparc.Application", {
               this.__mainPage = mainPage;
               this.__loadView(mainPage);
             };
-            if (osparc.wrapper.WebSocket.getInstance().isAppConnected()) {
+            const wsInstance = osparc.wrapper.WebSocket.getInstance();
+            if (wsInstance.isAppConnected()) {
               loadViewerPage();
             } else {
-              osparc.wrapper.WebSocket.getInstance().addListener("changeAppConnected", e => {
+              const listenerId = wsInstance.addListener("changeAppConnected", function(e) {
                 if (e.getData()) {
+                  wsInstance.removeListenerById(listenerId);
                   loadViewerPage();
                 }
               }, this);
@@ -528,11 +530,13 @@ qx.Class.define("osparc.Application", {
         this.__mainPage = mainPage;
         this.__loadView(mainPage);
       };
-      if (osparc.wrapper.WebSocket.getInstance().isAppConnected()) {
+      const wsInstance = osparc.wrapper.WebSocket.getInstance();
+      if (wsInstance.isAppConnected()) {
         loadNodeViewerPage();
       } else {
-        osparc.wrapper.WebSocket.getInstance().addListener("changeAppConnected", e => {
+        const listenerId = wsInstance.addListener("changeAppConnected", e => {
           if (e.getData()) {
+            wsInstance.removeListenerById(listenerId);
             loadNodeViewerPage();
           }
         }, this);

services/static-webserver/client/source/class/osparc/WatchDog.js

@@ -68,6 +68,10 @@ qx.Class.define("osparc.WatchDog", {
     },
   },
 
+  statics: {
+    DEFAULT_HEARTBEAT_INTERVAL: 2000, // default to 2 seconds
+  },
+
   members: {
     __clientHeartbeatWWPinger: null,
 
@@ -89,7 +93,7 @@ qx.Class.define("osparc.WatchDog", {
     },
 
     __startPinging: function() {
-      const heartbeatInterval = this.getHeartbeatInterval() || 2000; // default to 2 seconds
+      const heartbeatInterval = this.getHeartbeatInterval() || osparc.WatchDog.DEFAULT_HEARTBEAT_INTERVAL;
       this.__clientHeartbeatWWPinger.postMessage(["start", heartbeatInterval]);
     },