I have such a question because I no longer know what to do. I have a BOT on Suggestion to a certain channel. When I run the bot via Visual Studio Code, the bot runs and everything works. But as soon as I load a boot on heroku.com, the program suddenly writes an error:

files = files.filter(f => f.endsWith(".js"))

Someone could help me, I would be very happy. Have a nice day

Index.js is here:

client.once('ready', () => {
    console.log('Tutorial Bot is online!');
});

client.commands = new Discord.Collection()
const fs = require("fs")
fs.readdir("./commands/", (error, files) => {
    files = files.filter(f => f.endsWith(".js"))
    files.forEach(f => {
        const command = require(`./commands/${f}`)
        client.commands.set(command.name, command)
        console.log(`Command ${command.name} was loaded!`)
    });
});

client.on("message", message => {
    if (message.author.bot) return;
    if (message.channel.type === "dm") return;
    if (!message.content.startsWith(config.prefix)) return;
    const args = message.content.slice(config.prefix.length).split(" ")
    const command = args.shift()
    const cmd = client.commands.get(command)
    if (cmd) {
        cmd.run(client, message, args)
    } else return;
});


bot.login(config.token);

Suggest.js is here

const { MessageEmbed } = require("discord.js");

module.exports = {
    name: "suggest",
    aliases: [],
    description: "Make a suggestion and have the community vote",
    category: "utility",
    usage: "suggest <suggestion>",
    run: async (client, message, args) => {
        let suggestion = args.slice(0).join(" ");
        let SuggestionChannel = message.guild.channels.cache.find(channel => channel.name === "suggestions");
        if (!SuggestionChannel) return message.channel.send("Please create a channel named suggestions before using this command!");
        const embed = new MessageEmbed()
            .setTitle("New Suggestion")
            .setDescription(suggestion)
            .setColor("RANDOM")
            .setFooter(`${message.author.tag} | ID: ${message.author.id}`)
            .setTimestamp()
        SuggestionChannel.send(embed).then(msg => {
            msg.react("👍🏼")
            msg.react("👎🏼")
        message.channel.send("Your suggestion has been sent!");
        });
    }
}