Storing data with Keyv

Keyv is a simple key-value store that works with multiple backends. It's fully scalable for sharding and supports JSON storage.

Installation

npm install --save keyv

Keyv requires an additional package depending on which persistent backend you would prefer to use. If you want to keep everything in memory, you can skip this part. Otherwise, install one of the below.

npm install --save @keyv/redis
npm install --save @keyv/mongo
npm install --save @keyv/sqlite
npm install --save @keyv/postgres
npm install --save @keyv/mysql

Now that Keyv and any necessary drivers are installed, create an instance of Keyv.

const Keyv = require('keyv');

// One of the following
const keyv = new Keyv(); // for in-memory storage
const keyv = new Keyv('redis://user:pass@localhost:6379');
const keyv = new Keyv('mongodb://user:pass@localhost:27017/dbname');
const keyv = new Keyv('sqlite://path/to/database.sqlite');
const keyv = new Keyv('postgresql://user:pass@localhost:5432/dbname');
const keyv = new Keyv('mysql://user:pass@localhost:3306/dbname');

Make sure to handle connection errors.

keyv.on('error', err => console.error('Keyv connection error:', err));

For more detailed setup, check out the Keyv readme.

Usage

Keyv exposes a familiar Map-like API. However, it only has set, get, delete, and clear methods. Additionally, instead of immediately returning data, these methods return Promises that resolve with the data.

(async () => {
	// true
	await keyv.set('foo', 'bar');

	// bar
	await keyv.get('foo');

	// undefined
	await keyv.clear();

	// undefined
	await keyv.get('foo');
})();

Application

Although Keyv can be used in any scenario where you need key-value data, we will focus on setting up a per-guild prefix configuration using Sqlite.

TIP

This section will still work with any provider supported by Keyv. We recommend PostgreSQL for larger applications.

Setup

const Discord = require('discord.js');
const Keyv = require('keyv');

const client = new Discord.Client();
const prefixes = new Keyv('sqlite://path/to.sqlite');
const globalPrefix = '.';

Command handler

This guide uses a very basic command handler with some added complexity to allow for multiple prefixes. For more a more robust command handler, look at the command handling guide.

client.on('message', async message => {
	if (message.author.bot) return;

	let args;
	// handle messages in a guild
	if (message.guild) {
		let prefix;

		if (message.content.startsWith(globalPrefix)) {
			prefix = globalPrefix;
		} else {
			// check the guild-level prefix
			const guildPrefix = await prefixes.get(message.guild.id);
			if (message.content.startsWith(guildPrefix)) prefix = guildPrefix;
		}

		// if we found a prefix, setup args; otherwise, this isn't a command
		if (!prefix) return;
		args = message.content.slice(prefix.length).split(/\s+/);
	} else {
		// handle DMs
		const slice = message.content.startsWith(globalPrefix) ? globalPrefix.length : 0;
		args = message.content.slice(slice).split(/\s+/);
	}

	// get the first space-delimited argument after the prefix as the command
	const command = args.shift().toLowerCase();
});

Prefix command

Now that you have a command handler, make a command to allow people to use your prefix system.

if (command === 'prefix') {
	// if there's at least one argument, set the prefix
	if (args.length) {
		await prefixes.set(message.guild.id, args[0]);
		return message.channel.send(`Successfully set prefix to \`${args[0]}\``);
	}

	return message.channel.send(`Prefix is \`${await prefixes.get(message.guild.id) || globalPrefix}\``);
}

You will probably want to setup additional validation such as required permissions and maximum prefix length.

Usage

User
User 11/21/2019
.prefix
Tutorial Bot
Tutorial Bot Bot 11/21/2019
Prefix is `.`
User
User 11/21/2019
.prefix $
Tutorial Bot
Tutorial Bot Bot 11/21/2019
Successfully set prefix to `$`
User
User 11/21/2019
$prefix
Tutorial Bot
Tutorial Bot Bot 11/21/2019
Prefix is `$`

Next steps

Keyv can be used in a variety of other applications, such as guild settings; simply create another instance with a different namespace for each setting. Additionally, it can be extended to work with whatever storage backend you prefer.

Check out the Keyv repository for more information.