How to use the @azure/event-hubs.EventPosition function in @azure/event-hubs

// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.

'use strict';

const logger = require('../lib').logger;
const config = require('../config');
const EventHubClient = require('@azure/event-hubs').EventHubClient;
const EventPosition = require('@azure/event-hubs').EventPosition;
const ServiceClient = require('azure-iothub').Client;
var serviceConnection = null;
var eventHubConnection = null;

// Called whenever an error occurs in either the message callback or the  eventhub connection setup
function errorCb(err) {
  logger.crit(err.message);
};

// Called whenever we receive a telemetry message from the client
function messageReceivedCb(message) {
  logger.debug('Service successfully received telemetry from client.');
  logger.trace(JSON.stringify(message));
  var targetDevice = message.body.toString();

  if(!targetDevice) {

const client = await event_hubs_1.EventHubClient.createFromIotHubConnectionString(IOT_HUB_CONNECTION_STRING);
    const hubInfo = await client.getHubRuntimeInformation();
    console.log(`Connected to IoT Hub at ${hubInfo.path}`);
    client.receive('1', (eventData) => {
        if (eventData.annotations) {
            const enqueuedTime = eventData.annotations['x-opt-enqueued-time'];
            console.debug(`Received message from IoT Hub, enqueued at ${enqueuedTime}`);
        }
        else {
            console.debug(`Received message from IoT Hub`);
        }
        db_1.updateState(eventData.body);
    }, (error) => {
        console.error(`Error receiving message from Event Hubs: ${error}`);
    }, {
        eventPosition: event_hubs_1.EventPosition.fromEnqueuedTime(Date.now())
    });
}
function getConfig(deviceId, cb) {