I am using the latest node.js and discord.js versions and I am coding on VSC. My bot started responding to all prefixes and I don't know why. The code I have currently:

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

client.commands = new Discord.Collection();

const commandFiles = fs.readdirSync('./commands/').filter(file => file.endsWith('.js'));
for(const file of commandFiles){
    const command = require(`./commands/${file }`);

    client.commands.set(command.name, command)
}

const PREFIX = '$';
 
 
client.on('ready', () => {
    console.log('updated');
})

client.on('message', message => {
 
    const args = message.content.substring(PREFIX.length).split(" ");

    switch (args[0]) {
        case 'ping':
            message.channel.send('pong!');
            break;
    }
});
 
        client.login(token);

However, with this code in mind, the bot still responds to any prefix. In the image below, I sent the ping command with various random letters and symbols in all at the same time. The bot responded pong to all of them.

not sure what is wrong as I am still new to discord.js but I cannot figure it out.