onValue 多次触发

Question

I'm using Node.js v18.12.1 and Discord.js v14. for developing the Discord bot. I need to read some data from Firebase. I'm confused because I'm used to how Java with Hibernate fetches data differently. Here, I need to use onValue() listener.

My onValue() acts strange. Instead of just reading the data from Firebase, it skips entirely, then it triggers multiple times, each time skipping the body block of its code, and then it actually does the code after.

I've read somewhere on this forum that this can happen because there are more onValue() listeners that are subscribed and they are all fired up. Someone mentioned I need to use the off() function somewhere "before" the onValue() . This confuses me because I'm using this listener in many locations. I need it in each command file, in execute(interaction) functions. You know, when you need to execute slash commands in Discord. I have it something like this:

async execute(interaction) {
    const infographicRef = ref(db, '/infographics/arena/' + interaction.options.getString("arena-team"));
    var imageUrl = null;
    var postUrl = null;

    onValue(infographicRef, (snapshot) => {
        imageUrl = snapshot.child("image-url").val();
        
        interaction.reply(imageUrl);
    })
},

And I planned for each command, in each command.js file to have onValue() . I'm not sure exactly what to do.

Also, I tried to work around this with once() method, I see it in Firebase documentation, but I got the error: ref.once() is not a function .

It seems that after first triggering of onValue method when the body is not executed, my code in interactionCreate.js is triggered as well, it points for a command to be executed again:

const { Events } = require('discord.js');

module.exports = {
    name: Events.InteractionCreate,
    async execute(interaction) {
        if (!interaction.isChatInputCommand()) return;

        const command = interaction.client.commands.get(interaction.commandName);

        if (!command) {
            console.error(`No command matching ${interaction.commandName} was found.`);
            return;
        }

        try {
            await command.execute(interaction);
        } catch (error) {
            console.error(`Error executing ${interaction.commandName}`);
            console.error(error);
        }
    },
};

my bot.js (which is in my case an index file)

const fs = require('node:fs');
const path = require('node:path');
const { Client, Collection, Events, GatewayIntentBits } = require('discord.js');
const { token } = require('./config.json');

const client = new Client({ intents: [GatewayIntentBits.Guilds] });

const eventsPath = path.join(__dirname, 'events');
const eventFiles = fs.readdirSync(eventsPath).filter(file => file.endsWith('.js'));

for (const file of eventFiles) {
    const filePath = path.join(eventsPath, file);
    const event = require(filePath);
    if (event.once) {
        client.once(event.name, (...args) => event.execute(...args));
    } else {
        client.on(event.name, (...args) => event.execute(...args));
    }
}


client.commands = new Collection();
const commandsPath = path.join(__dirname, 'commands');
const commandFiles = fs.readdirSync(commandsPath).filter(file => file.endsWith('.js'));



for (const file of commandFiles) {
    const filePath = path.join(commandsPath, file);
    const command = require(filePath);
    client.commands.set(command.data.name, command);
}

client.once(Events.ClientReady, () => {
    console.log('Ready!');
});


client.on(Events.InteractionCreate, async interaction => {
    if (!interaction.isChatInputCommand()) return;

    const command = client.commands.get(interaction.commandName);

    if (!command) return;

    try {
        await command.execute(interaction);
    } catch (error) {
        console.error(error);
        await interaction.reply({ content: 'There was an error while executing this command!', ephemeral: true });
    }
});

client.login(token);

Answer 1

The onValue function registers a realtime listener, that continues to monitor the value on the database.

If you want to read a value once, that'd be done with get() function in v9 (which is the equivalent of the once method in earlier SDK versions). Have a look at the code sample in the documentation on reading data once .