server.js

var Discord = require("discord.js");
var bot = new Discord.Client();
var mtrAggregator = new require("./aggregators/rules/mtr.js");
var ipgAggregator = new require("./aggregators/rules/ipg.js");
var crAggregator = new require("./aggregators/rules/cr.js");
var jarAggregator = new require("./aggregators/rules/jar.js");
var cardAggregator = new require("./aggregators/mtg_cards/cards.js");

const mtr = "!mtr";
const ipg = "!ipg";
const cr = "!cr";
const jar = "!jar";
const card = "!card";
const help = "!help";

/**
 * @param msg.channel.sendMessage
 */
bot.on("message", msg => {
	if(bot.user.id === msg.author.id) {return;}
	const query = msg.content.split(" ");
	const command = query[0].toLowerCase();
	const parameter = query.length > 1 ? query.slice(1).join(" ") : "";
	switch(command){
		case mtr:
			new mtrAggregator().getContent(parameter,respondToMsg);
			break;
        case ipg:
            new ipgAggregator().getContent(parameter,respondToMsg);
            break;
        case cr:
            new crAggregator().getContent(parameter,respondToMsg);
            break;
        case jar:
            new jarAggregator().getContent(parameter,respondToMsg);
            break;
		case card:
		    new cardAggregator().getContent(parameter,respondToMsg);
			break;
        case help:
            //todo
            break;
	}
	function respondToMsg(response) {
        if(response){
            msg.channel.sendMessage(response);
        }
	}
});

bot.on('ready', () => {
  console.log('I am ready!', bot.user.username);
});

bot.login(process.env.DISCORD_TOKEN);