<!DOCTYPE html>
<html>
    <head>
        <script>
        function postMessage(event) {
            window.webkit.messageHandlers.testHandler.postMessage(event.type);

        }
        window.addEventListener('load', event => {
            video.addEventListener('loadeddata', postMessage);
            video.addEventListener('suspend', postMessage);
            video.src = 'video-with-audio.mp4';
        });
        </script>
    <body>
        <video id=video></video>
</script></body></html>"