[RN] Clarify, simplify the source code

react/features/app/reducer.js

 
 import { APP_WILL_MOUNT, APP_WILL_UNMOUNT } from './actionTypes';
 
-/**
- * The initial Redux state of features/app.
- */
-const INITIAL_STATE = {
-    /**
-     * The one and only (i.e. singleton) App instance which is currently
-     * mounted.
-     *
-     * @type {App}
-     */
-    app: undefined
-};
-
-ReducerRegistry.register('features/app', (state = INITIAL_STATE, action) => {
+ReducerRegistry.register('features/app', (state = {}, action) => {
     switch (action.type) {
     case APP_WILL_MOUNT:
         if (state.app !== action.app) {
             return {
                 ...state,
+
+                /**
+                 * The one and only (i.e. singleton) App instance which is
+                 * currently mounted.
+                 *
+                 * @type {App}
+                 */
                 app: action.app
             };
         }
         if (state.app === action.app) {
             return {
                 ...state,
-                app: INITIAL_STATE.app
+                app: undefined
             };
         }
         break;

react/features/base/lib-jitsi-meet/functions.js

  * Loads config.js file from remote server.
  *
  * @param {string} host - Host where config.js is hosted.
- * @param {string} configLocation='/config.js' - Relative pah to config.js file.
+ * @param {string} path='/config.js' - Relative pah to config.js file.
  * @returns {Promise<Object>}
  */
-export function loadConfig(host, configLocation = '/config.js') {
-    return loadScript(new URL(configLocation, host).toString())
+export function loadConfig(host, path = '/config.js') {
+    return loadScript(new URL(path, host).toString())
         .then(() => {
             const config = window.config;
 
 
             return config;
         })
-        .catch(error => {
-            console.error(
-                    `Failed to load ${configLocation} from ${host}`,
-                    error);
+        .catch(err => {
+            console.error(`Failed to load ${path} from ${host}`, err);
 
-            throw error;
+            throw err;
         });
 }

react/features/base/lib-jitsi-meet/reducer.js

             };
 
         case SET_CONFIG:
-            return {
-                ...state,
-                config: {
-                    ...action.config,
-                    ...state.config
-                }
-            };
+            return _setConfig(state, action);
 
         default:
             return state;
         }
     });
+
+/**
+ * Reduces a specific Redux action SET_CONFIG of the feature
+ * base/lib-jitsi-meet.
+ *
+ * @param {Object} state - The Redux state of the feature base/lib-jitsi-meet.
+ * @param {Action} action - The Redux action SET_CONFIG to reduce.
+ * @private
+ * @returns {Object} The new state of the feature base/lib-jitsi-meet after the
+ * reduction of the specified action.
+ */
+function _setConfig(state, action) {
+    return {
+        ...state,
+        config: {
+            // The final config is the result of augmenting the default config
+            // with whatever the deployment has chosen to override/overwrite.
+            ...INITIAL_STATE.config,
+            ...action.config
+        }
+    };
+}