a twitch bot with a command to add, remove and edit the alias of a 7tv emote

const tmi = require('tmi.js');
const fs = require('fs');

const opts = {
  identity: {
    username: process.env.BOT_USERNAME,
    password: process.env.OAUTH_TOKEN
  },
  channels: [
    process.env.CHANNEL_NAME
  ]
};

const client = new tmi.client(opts);
client.connect();

client.on('message', onMessageHandler);

function onMessageHandler(target, context, msg, self) {
  if (self) { return; } // Ignore messages from the bot
  
  const commandName = msg.trim();
  const dir = `${__dirname}/data`;

  if (commandName.substr(0, 1) !== '!') {
     return;
  }
  
  if (commandName === '!alias') {
    fs.readFile(`${dir}/${context.username}.json`, (err, data) => {
      if (err) {