discord-bot-build

Overview

Build a Discord bot with slash commands, event handlers, and moderation capabilities using discord.js. The bot runs as a Node.js process and connects to Discord via the Gateway.

When to Use

• The user wants a Discord bot for their server.
• The user wants to automate moderation, send announcements, or add custom commands.
• The user says "build a Discord bot", "make a bot for my server", or "I need a Discord mod bot".

Prerequisites

1. Node.js 18+ — check with node --version
2. A Discord bot token — create a bot at https://discord.com/developers/applications
3. Privileged Gateway Intents — enable in the Developer Portal:
   • Presence Intent (if you need online/offline tracking)
   • Server Members Intent (if you need member lists)
   • Message Content Intent (required for reading message text)

Bot Setup

Step 1: Create the application

1. Go to https://discord.com/developers/applications
2. Click "New Application" → name it → go to the "Bot" tab
3. Click "Add Bot" → copy the token (keep it secret)
4. Under "Privileged Gateway Intents", enable Message Content Intent
5. Under "OAuth2 → URL Generator", select bot + applications.commands scopes and the permissions you need
6. Open the generated URL to invite the bot to your server

Step 2: Initialize the project

mkdir my-bot && cd my-bot
npm init -y
npm install discord.js dotenv

Step 3: Create the bot file

// index.js
const { Client, GatewayIntentBits, SlashCommandBuilder, Events } = require('discord.js');
require('dotenv').config();

const client = new Client({
    intents: [
        GatewayIntentBits.Guilds,
        GatewayIntentBits.GuildMessages,
        GatewayIntentBits.MessageContent,
        GatewayIntentBits.GuildMembers,
    ],
});

client.once(Events.ClientReady, c => {
    console.log(`Logged in as ${c.user.tag}`);
});

// Register slash commands
client.on(Events.InteractionCreate, async interaction => {
    if (!interaction.isChatInputCommand()) return;

    if (interaction.commandName === 'ping') {
        await interaction.reply('Pong!');
    }

    if (interaction.commandName === 'kick') {
        const target = interaction.options.getUser('user');
        const reason = interaction.options.getString('reason') ?? 'No reason provided';
        if (!interaction.memberPermissions.has('KickMembers')) {
            await interaction.reply('You do not have permission to kick members.');
            return;
        }
        try {
            await interaction.guild.members.kick(target, reason);
            await interaction.reply(`Kicked ${target.tag} for: ${reason}`);
        } catch (error) {
            await interaction.reply(`Failed to kick: ${error.message}`);
        }
    }
});

client.login(process.env.DISCORD_TOKEN);

Step 4: Create .env

DISCORD_TOKEN=your_bot_token_here

Step 5: Register slash commands

// deploy-commands.js
const { REST, Routes, SlashCommandBuilder } = require('discord.js');
require('dotenv').config();

const commands = [
    new SlashCommandBuilder()
        .setName('ping')
        .setDescription('Replies with pong'),
    new SlashCommandBuilder()
        .setName('kick')
        .setDescription('Kick a member')
        .addUserOption(opt => opt.setName('user').setDescription('The user to kick').setRequired(true))
        .addStringOption(opt => opt.setName('reason').setDescription('Reason for kicking')),
].map(cmd => cmd.toJSON());

const rest = new REST().setToken(process.env.DISCORD_TOKEN);

(async () => {
    try {
        await rest.put(Routes.applicationCommands(process.env.CLIENT_ID), { body: commands });
        console.log('Slash commands registered.');
    } catch (error) {
        console.error(error);
    }
})();

Run once: node deploy-commands.js

Step 6: Start the bot

node index.js

Command Registration

Commands must be registered before they appear in Discord. Two scopes:

For development, use guild commands (instant). For production, use global commands.

// Guild command (instant, for testing)
await rest.put(
    Routes.applicationGuildCommands(clientId, guildId),
    { body: commands }
);

// Global command (production, up to 1hr delay)
await rest.put(
    Routes.applicationCommands(clientId),
    { body: commands }
);

Event Handling

// Member joined
client.on(Events.GuildMemberAdd, member => {
    const channel = member.guild.systemChannel;
    if (channel) channel.send(`Welcome ${member} to the server!`);
});

// Message deleted
client.on(Events.MessageDelete, message => {
    console.log(`Message deleted in #${message.channel.name}: ${message.content}`);
});

// Reaction added
client.on(Events.MessageReactionAdd, (reaction, user) => {
    if (reaction.emoji.name === '📌') {
        // Pin the message
        reaction.message.pin();
    }
});

Moderation Commands

Keeping the Bot Running

With PM2 (recommended):

npm install -g pm2
pm2 start index.js --name my-bot
pm2 save
pm2 startup  # auto-restart on reboot

With Docker:

FROM node:20-slim
WORKDIR /app
COPY package*.json ./
RUN npm ci --production
COPY . .
CMD ["node", "index.js"]

Common Pitfalls

1. Message Content Intent not enabled. The bot can't read message text without this. Enable it in the Developer Portal under "Privileged Gateway Intents" — without it, message.content is always empty even though the event still fires.
2. Token committed or leaked. Never commit the .env file — add it to .gitignore. If the token leaks, regenerate it immediately in the Developer Portal; a leaked token gives full control of the bot.
3. Commands not appearing after deploy. Global commands take up to 1 hour to propagate. Use guild commands (applicationGuildCommands) for testing since they're instant. Also re-run deploy-commands.js after adding or changing any command definition — editing index.js alone doesn't re-register them.
4. Bot can't kick/ban despite having the permission. The bot's role must sit higher in the role hierarchy than the target user's highest role, in addition to having the Kick/Ban permission — Discord enforces hierarchy regardless of permission flags.
5. Rate limits on bulk operations. Discord enforces per-route rate limits. Bulk operations (mass ban, mass delete) should use bulkDelete and expect the library's automatic rate-limit handling to introduce delays — don't assume every call completes instantly.
6. No error handling crashes the whole bot. An unhandled exception inside an interaction handler can crash the process if not caught. Always wrap command logic in try/catch and reply with the error so the user gets feedback instead of a silently dead bot.

Verification Checklist

• node index.js logs "Logged in as ..." with no uncaught errors on startup
• deploy-commands.js was run and slash commands appear in Discord (guild commands show instantly; confirm before assuming global propagation)
• Message Content Intent is enabled in the Developer Portal if any command reads message.content
• .env is listed in .gitignore and the token was never committed
• Moderation commands (/kick, /ban, etc.) were tested against a low-permission test account, confirming both the permission check and the Discord role-hierarchy behavior
• Every interaction handler has a try/catch that replies with an error message instead of leaving the interaction unanswered