<script>
    async function enumerate(event)
    {
        let devices = await navigator.mediaDevices.enumerateDevices();
        let visible = devices.map(device => device.kind.indexOf('video') == 0 ? 'camera' : 'microphone').sort();
        visible = visible.join('+');
        parent.postMessage(`${event.data}:${visible}`, '*');
        result.innerHTML = visible;
    }

    window.addEventListener("message", (id) => enumerate(id));
</script>

<div id='result'></div>