TypeError?

rx-6.js

import { from } from 'rxjs'

// This is the observable that is going to be emitted once the connection/subscription has been made.  This will need to be subscribed to in order to receive actual messages.
const listener = client =>
  // This used to be Observable.create(observer => ...)
	from(observer => {
		client.on('message', (topic, message) =>
			observer.next(JSON.parse(message.toString()))
		)
		return () => {
			// Remove event listeners
			client.removeAllListeners('message')
		}
	})

// This return an observable that will attempt to connect to a MQTT client.  However, this observable is simply dealing with connection, not with messages.  The only emitted item from this observable is another observable that could be listened to for messages
export default (topic, endpoint, { region, credentials }) => {
  // This used to be Observable.create(observer => ...)
	return from(observer => {
		let client = null
		Promise.all([import('aws-mqtt'), import('aws-sdk/global')]).then(
			([AWSMqtt, { config }]) => {
				config.update({
					region,
					credentials,
				})
				client = AWSMqtt.connect({
					WebSocket: window.WebSocket,
					region,
					endpoint,
					credentials,
					connectTimeout: 30 * 1000,
				})
				client.on('connect', () => {
					client.subscribe(`${topic}`, { qos: 1 }, err => {
						if (err) {
							observer.error(err)
						} else {
							// Send back another observable to be subscribed to
							observer.next(listener(client))
						}
					})
				})
				client.on('error', err => observer.error(err))
			}
		)
		return () => {
			client && client.end()
			observer.complete()
		}
	})
}