bot.js

'use strict'

// Slack's Realtime Messaging Client
const RtmClient       = require('@slack/client').RtmClient;
const MemoryDataStore = require('@slack/client').MemoryDataStore;

// Slack's event name constants
const RTM_EVENTS    = require('@slack/client').RTM_EVENTS;
const CLIENT_EVENTS = require('@slack/client').CLIENT_EVENTS;

class Bot {
    constructor(opts) {
        let slackToken = opts.token;
        let autoReconnect = opts.autoReconnect || true;
        let autoMark = opts.autoMark || true;

        // Construct the Slack client
        this.slack = new RtmClient(slackToken, {
            logLevel: 'error',
            dataStore: new MemoryDataStore(),
            autoReconnect: autoReconnect,
            autoMark: autoMark
        });
        
        this.keywords = new Map();
        
        this.slack.on(RTM_EVENTS.MESSAGE, (message) => {
            // Only process text messages
            if (!message.text) {
                return;
            }

            let channel = this.slack.dataStore.getChannelGroupOrDMById(message.channel);
            let user    = this.slack.dataStore.getUserById(message.user);

            // Test each keyword's regex and set callback for each match
            for (let regex of this.keywords.keys()) {
                if (regex.test(message.text)) {
                    let callback = this.keywords.get(regex);
                    callback(message, channel, user);
                }
            }

        }
    }

    respondTo(keywords, callback, start) {
        if (start) {
            keywords = '^' + keywords;
        }

        let regex = new RegExp(keywords, 'i');

        this.keywords.set(regex, callback);
    }

    send(message, channel, callback) {
        this.slack.sendMessage(message, channel.id, () => {
            if (callback) {
                callback();
            }
        });
    }

}

module.exports = Bot;

index.js

'use strict'

let Bot = require('./bot');

const Bot = new Bot({
    token: process.env.SLACK_TOKEN,
    autoReconnect: true,
    autoMark: true
});

bot.respondTo('hello', (message, channel, user) => {
    bot.send(`Kon\'nichiwa, ${user.name}!`, channel)
}, true);