flow(AbstractAudio): specific function types

react/features/base/media/components/AbstractAudio.js

  * playback.
  */
 export type AudioElement = {
-    pause: Function,
-    play: Function,
-    setSinkId: ?Function
-}
+    pause: () => void,
+    play: () => void,
+    setSinkId?: string => void
+};
 
 /**
  * {@code AbstractAudio} component's property types.
      * A callback which will be called with {@code AbstractAudio} instance once
      * the audio element is loaded.
      */
-    setRef: ?Function,
+    setRef?: ?AudioElement => void,
 
     /**
      * The URL of a media resource to use in the element.
         this.setAudioElementImpl = this.setAudioElementImpl.bind(this);
     }
 
+    pause: () => void;
+
     /**
      * Attempts to pause the playback of the media.
      *
      * @public
      * @returns {void}
      */
-    pause() {
+    pause(): void {
         this._audioElementImpl && this._audioElementImpl.pause();
     }
 
+    play: () => void;
+
     /**
      * Attempts to being the playback of the media.
      *
      * @public
      * @returns {void}
      */
-    play() {
+    play(): void {
         this._audioElementImpl && this._audioElementImpl.play();
     }
 
-    setAudioElementImpl: (?AudioElement) => void;
+    setAudioElementImpl: ?AudioElement => void;
 
     /**
      * Set the (reference to the) {@link AudioElement} object which implements
      * @protected
      * @returns {void}
      */
-    setAudioElementImpl(element: ?AudioElement) {
+    setAudioElementImpl(element: ?AudioElement): void {
         this._audioElementImpl = element;
 
         // setRef
         const { setRef } = this.props;
 
+        // $FlowFixMe
         typeof setRef === 'function' && setRef(element ? this : null);
     }
 
+    setSinkId: string => void;
+
     /**
      * Sets the sink ID (output device ID) on the underlying audio element.
      * NOTE: Currently, implemented only on Web.
      * @param {string} sinkId - The sink ID (output device ID).
      * @returns {void}
      */
-    setSinkId(sinkId: String) {
+    setSinkId(sinkId: string): void {
         this._audioElementImpl
             && typeof this._audioElementImpl.setSinkId === 'function'
             && this._audioElementImpl.setSinkId(sinkId);

react/features/chat/constants.js

-/* eslint-disable no-unused-vars */
-import { playAudio } from '../base/media';
-
 /**
  * The audio ID of the audio element for which the {@link playAudio} action is
  * triggered when new chat message is received.
+ *
  * @type {string}
  */
 export const INCOMING_MSG_SOUND_ID = 'INCOMING_MSG_SOUND';

react/features/chat/middleware.js

  */
 MiddlewareRegistry.register(store => next => action => {
     switch (action.type) {
-    case APP_WILL_MOUNT: {
-        // Register chat msg sound only on web
-        typeof APP !== 'undefined'
-            && store.dispatch(
+    case APP_WILL_MOUNT:
+        // Register the chat message sound on Web only because there's no chat
+        // on mobile.
+        typeof APP === 'undefined'
+            || store.dispatch(
                 registerSound(INCOMING_MSG_SOUND_ID, INCOMING_MSG_SOUND_SRC));
         break;
-    }
-    case APP_WILL_UNMOUNT: {
-        // Register chat msg sound only on web
-        typeof APP !== 'undefined'
-            && store.dispatch(unregisterSound(INCOMING_MSG_SOUND_ID));
+
+    case APP_WILL_UNMOUNT:
+        // Unregister the chat message sound on Web because it's registered
+        // there only.
+        typeof APP === 'undefined'
+            || store.dispatch(unregisterSound(INCOMING_MSG_SOUND_ID));
         break;
-    }
+
     case CONFERENCE_JOINED:
-        typeof APP !== 'undefined'
-            && _addChatMsgListener(action.conference, store);
+        typeof APP === 'undefined'
+            || _addChatMsgListener(action.conference, store);
         break;
     }
 
  * new event listener will be registered.
  * @param {Dispatch} next - The redux dispatch function to dispatch the
  * specified action to the specified store.
- * @returns {void}
  * @private
+ * @returns {void}
  */
 function _addChatMsgListener(conference, { dispatch }) {
-    // XXX Currently there's no need to remove the listener, because
-    // conference instance can not be re-used. Listener will be gone with
-    // the conference instance.
+    // XXX Currently, there's no need to remove the listener, because the
+    // JitsiConference instance cannot be reused. Hence, the listener will be
+    // gone with the JitsiConference instance.
     conference.on(
         JitsiConferenceEvents.MESSAGE_RECEIVED,
         () => {
-            if (!APP.UI.isChatVisible()) {
-                dispatch(playSound(INCOMING_MSG_SOUND_ID));
-            }
+            APP.UI.isChatVisible()
+                || dispatch(playSound(INCOMING_MSG_SOUND_ID));
         });
 }

react/features/chat/sounds.web.js

 /**
  * The audio source for the incoming chat message sound.
+ *
  * @type {string}
  */
 export const INCOMING_MSG_SOUND_SRC = 'sounds/incomingMessage.wav';