Application commands are not updated in chat, but in "Manage Integration" are up-to-date.

client.commands = new Map();
const commandPath = './commands';
const commandFiles = fs.readdirSync(commandPath).filter((file) => file.endsWith('.mjs'));
for (const file of commandFiles) {
    const filePath = './' + path.join(commandPath, file);
    let command = await import(filePath);
    command = command.default;

    if (command.ignore) continue;
    if (command.data && command.execute) {
        client.commands.set(command.data.name, command);
    } else {
        console.error(`Error: ${filePath} command is missing a required property "data" or "execute"`);
    }
}

import { Client, Events } from 'discord.js';

export default {
    once: true,
    name: Events.ClientReady,

    /**
     * execute
     * @param {Client} client 
     */
    async execute(client) {
        console.info('Client is Ready');

        // load commands
        const commands = Array.from(client.commands.values()).map(command => command.data.toJSON());
        client.application.commands.set(commands)
            .catch(console.error);
        
        const commandNames = commands.map(command => command.name);
        console.info(`Commands loaded: ${commandNames.join(', ')}`);
    },
};

import { SlashCommandBuilder, CommandInteraction } from 'discord.js';

export default {
    data: new SlashCommandBuilder()
        .setName('ping')
        .setDescription('Reply with ms'),
    
    /**
     * execute
     * @param {CommandInteraction} interaction 
     */
    async execute(interaction) {
        await interaction.reply(`🏓 Ping! ${interaction.client.ws.ping}ms`);
    },
};