Use V5SerialDevice for most applications. It finds compatible ports, verifies the device, refreshes state, and exposes high-level views. 
import { V5SerialDevice } from "@v5x/serial";

const device = new V5SerialDevice(navigator.serial);

try {
  const connected = await device.connect();
  if (!connected) throw new Error("Connection was not established");

  console.log(device.isConnected);
  await device.refresh();
} finally {
  await device.dispose();
}
disconnect() closes the current port. dispose() also disables automatic refresh and reconnect behavior and clears the internal timer. Use dispose() when the instance will not be reused. Set autoReconnect, autoRefresh, or pauseRefreshOnFileTransfer before connecting when the defaults do not fit the application.