Detect Capabilities

const cameraList = await TRTC.getCameraList();
const hasCameraDevice = cameraList.length > 0;

if (!hasCameraDevice) {
    // User has not any camera.
}

try {
    // Capture and play camera, not need to publish stream
    await trtc.startLocalVideo({ view: 'camera-video-view-id', publish: false });
} catch(error) {
    // Common reasons: NotAllowedError or NotReadableError
}

// You can get the cameraId from the camera list you got in fisrt step.
if (cameraList[1]) {
    try {
        await trtc.updateLocalVideo({ option: { cameraId: cameraList[1].deviceId } });
    } catch(error) {
      // Common reasons: NotAllowedError or NotReadableError, same with step 2.
    }
}

await trtc.stopLocalVideo();

const microphoneList = await TRTC.getMicrophoneList();
const hasMicrophoneDevice = micList.length > 0;

if (!hasMicrophoneDevice) {
    // User has not any microphone.
}

try {
    // Capture microphone
    await trtc.startLocalAudio({ publish: false });
    trtc.on(TRTC.EVENT.AUDIO_VOLUME, event => {
        event.result.forEach(({ userId, volume }) => {
            // When userId is an empty string, it represents the volume of the local microphone.
            const isMe = userId === ''; 
            if (isMe) {
               // show a volume bar based on the value of volume.
            }
        })
    });
    trtc.enableAudioVolumeEvaluation(500);
} catch(error) {
    // Common reasons: NotAllowedError or NotReadableError
}

// You can get the microphoneId from the microphone list you got in fisrt step.
if (microphoneList[1]) {
    try {
        await trtc.updateLocalAudio({ option: { microphoneId: microphoneList[1].deviceId } });
    } catch(error) {
      // Common reasons: NotAllowedError or NotReadableError, same with step 2.
    }
}

// You need to stop microphone when the testing finished.
await trtc.stopLocalAudio();
// disable audio-volume event
trtc.enableAudioVolumeEvaluation(-1);

const speakerList = await TRTC.getSpeakerList();
if (speakerList.length === 0) {
    // User has not speaker.
}

<audio id="audio-player" src="xxxxx" controls></audio>

const audioElement = document.getElementById('audio-player');
if (speakerList[1]) {
    audioElement.sinkId = speakerList[1].deviceId;
}