Notify End Of Play From Objective C To Javascript WKWebkit AVPlayer

I am trying to get a notification passed from ObjC to JavaScript when my audio has finished playing.

I currently call Obj C to play audio like so (from JS):

window.webkit.messageHandlers.playLetter.postMessage(audioSrc);

On the ObjC side I have the following method:

- (void) userContentController:(WKUserContentController *)userContentController didReceiveScriptMessage:(WKScriptMessage *)scriptMessage {

   if([scriptMessage.name isEqualToString:@“playLetter”]){
       _contentAudioPlayer = [[AVPlayer alloc] initWithURL:[NSURL URLWithString:scriptMessage.body]];
       [_contentAudioPlayer play];

       [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(playerItemDidReachEnd) name:AVPlayerItemDidPlayToEndTimeNotification object:_contentAudioPlayer.currentItem];
   }
}

and the notification center calls this method when the audio has ended playing:

- (void) playerItemDidReachEnd {
    NSLog(@"audio ended");
}

Which is successful each time the audio ends.

My question is:

How can I notify my JavaScript that the audio has ended? On the JS side, I need to "wait" for the end of the audio to carry on the intended course of action

If you need more info please let me know.

Thx in advance.

I created a custom event on the JavaScript side of my application and dispatched the event in the playerItemDidReachEnd method with evaluateJavaScript from the webView:

- (void) playerItemDidReachEnd {
   [_webView evaluateJavaScript:
    @“var event = new CustomEvent(‘letterplayed’, {\n”
    @” detail: {\n”
    @”     message: ‘letter audio had finished playing’,\n”
    @”     time: new Date(),\n”
    @” },\n”
    @” bubbles: true,\n”
    @” cancelable: true\n”
    @“});\n”
    @“window.dispatchEvent(event);”
              completionHandler:nil];
}