How to use the mediasoup-client.Device function in mediasoup-client

const handleRouterRtpCapabilitiesRequest = async (jsonMessage) => {
  const { routerRtpCapabilities, sessionId } = jsonMessage;
  console.log('handleRouterRtpCapabilities() [rtpCapabilities:%o]', routerRtpCapabilities);

  try {
    const device = new mediasoup.Device();
    // Load the mediasoup device with the router rtp capabilities gotten from the server
    await device.load({ routerRtpCapabilities });

    peer = new Peer(sessionId, device);
    createTransport();
  } catch (error) {
    console.error('handleRouterRtpCapabilities() failed to init device [error:%o]', error);
    socket.close();
  }
};

export async function main() {
  console.log(`starting up ... my peerId is ${myPeerId}`);
  try {
    device = new mediasoup.Device();
  } catch (e) {
    if (e.name === 'UnsupportedError') {
      console.error('browser not supported for video calls');
      return;
    } else {
      console.error(e);
    }
  }

  // use sendBeacon to tell the server we're disconnecting when
  // the page unloads
  window.addEventListener('unload', () => sig('leave', {}, true));
}

async function loadDevice(routerRtpCapabilities) {
  try {
    device = new mediasoup.Device();
  } catch (error) {
    if (error.name === 'UnsupportedError') {
      console.error('browser not supported');
    }
  }
  await device.load({ routerRtpCapabilities });
}

const socketRequest = SocketPromise(socket);
  const uiVCodecName = document.querySelector(
    "input[name='uiVCodecName']:checked"
  ).value;
  const response = await socketRequest({
    type: "START_MEDIASOUP",
    vCodecName: uiVCodecName
  });
  const routerRtpCapabilities = response.data;

  console.log("[server] mediasoup router created");

  let device = null;
  try {
    device = new MediasoupClient.Device();
  } catch (err) {
    if (err.name === "UnsupportedError") {
      console.error("mediasoup-client doesn't support this browser");
      return;
    }
  }
  global.mediasoup.device = device;

  try {
    await device.load({ routerRtpCapabilities });
  } catch (err) {
    if (err.name === "InvalidStateError") {
      console.warn("mediasoup device was already loaded");
    }
  }

async function startMediasoup() {
  const socket = global.server.socket;

  const socketRequest = SocketPromise(socket);
  const response = await socketRequest({ type: "START_MEDIASOUP" });
  const routerRtpCapabilities = response.data;

  console.log("[server] mediasoup router created");

  let device = null;
  try {
    device = new MediasoupClient.Device();
  } catch (err) {
    if (err.name === "UnsupportedError") {
      console.error("mediasoup-client doesn't support this browser");
      return;
    }
  }
  global.mediasoup.device = device;

  try {
    await device.load({ routerRtpCapabilities });
  } catch (err) {
    if (err.name === "InvalidStateError") {
      console.warn("mediasoup device was already loaded");
    }
  }