How to add a prefix discord.js - discord

Question

require('dotenv').config();
const Discord = require('discord.js');
const bot = new Discord.Client();
const TOKEN = process.env.TOKEN;
const prefix = ".";
bot.login(TOKEN);
bot.on('ready', () => {
console.info(`Logged in as ${bot.user.tag}!`);
});
bot.on('message', msg => {
if (msg.content === 'ping') {
msg.channel.send('pong');
} else if (msg.content.startsWith('!kick')) {
if (msg.mentions.users.size) {
const taggedUser = msg.mentions.users.first();
msg.channel.send(`You wanted to kick: ${taggedUser.username}`);
} else {
msg.reply('Please tag a valid user!');
}
}
});
currently that is what im using im trying to make it so i have to type .pingto get the message Pong but i cant figure out how to get the prefix to use

Answer 1

You could use this code to get the command name:
bot.on('message', msg => {
const command = msg.content.slice(prefix.length).split(' ')[0]
if (command === 'ping') {
msg.channel.send('pong');
} else if (command === 'kick') {
if (msg.mentions.users.size) {
const taggedUser = msg.mentions.users.first();
msg.channel.send(`You wanted to kick: ${taggedUser.username}`);
} else {
msg.reply('Please tag a valid user!');
}
}
});
Note that this changes the kick command from !kick to .kick.
I recommend reading this section of the Discord.js guide for how to setup commands (and also user arguments if you need).

Answer 2

You can check for a concatenation of the prefix and the command name.
To check for .ping where prefix is .
if (msg.content === prefix + 'ping') {
// do something
}
To make it safer you can make it return early by checking if the message starts with the prefix.
if (!msg.content.startWith(prefix)) {
return;
}
This way when that check passes, you can slice away the prefix, and check the command name directly without having to worry about the prefix.
const commandName = msg.content.slice(prefix.length); // remove prefix character(s)
if (commandName === 'ping') {
// do something
}
All together it'd look like:
const prefix = '.'
bot.on('message', msg => {
// not start with prefix -> return early
if (!msg.content.startWith(prefix)) return;
// remove prefix to get command name
const commandName = msg.content.slice(prefix.length);
// check for command name directly
if (commandName === 'ping') {
// do something
} else if (commandName === 'kick') {
// do another thing
}
}