bot_discord.js

const Discord = require('discord.js');
const client = new Discord.Client();

client.on('ready', () => {
  console.log(Logged in as ${client.user.tag}!);
});

client.on('message', msg => {
  if (msg.content === '!ping') {
    msg.reply('Pong!');
  }
});

client.login('YOUR_BOT_TOKEN_HERE');