Edit in JSFiddle

import mqtt from 'async-mqtt';

const username = 'your_username';
const password = 'your_password';
const endpoint = 'mqtt://mqtt.spotto.cloud';

const connect = async () => {
  const connection = await mqtt.connectAsync(
    endpoint,
    {
      username,
      password,
    },
  );

  return connection;
};

const connection = connect();