How can I fix this ReferenceError when using .setSelfDeaf()?

Question

I'm trying to use .setSelfDeaf() in my code but I couldn't figure it out. Every way I tried ended up crashing the bot when executed.

Could someone help me to use it? I want is the bot the deafen itself every time it joins a voice channel.

Edit: added the error I am getting and the updated code upon request.

The error I am getting:

2021-03-04T06:25:06.238627+00:00 app[worker.1]: /app/code.js:53
2021-03-04T06:25:06.238628+00:00 app[worker.1]:     connection.voice.setSelfDeaf(true);
2021-03-04T06:25:06.238629+00:00 app[worker.1]:     ^
2021-03-04T06:25:06.238629+00:00 app[worker.1]: 
2021-03-04T06:25:06.238629+00:00 app[worker.1]: ReferenceError: connection is not defined
2021-03-04T06:25:06.238630+00:00 app[worker.1]:     at Client.<anonymous> (/app/code.js:53:5)
2021-03-04T06:25:06.238630+00:00 app[worker.1]:     at Client.emit (events.js:327:22)
2021-03-04T06:25:06.238631+00:00 app[worker.1]:     at VoiceStateUpdate.handle (/app/node_modules/discord.js/src/client/actions/VoiceStateUpdate.js:40:14)
2021-03-04T06:25:06.238632+00:00 app[worker.1]:     at Object.module.exports [as VOICE_STATE_UPDATE] (/app/node_modules/discord.js/src/client/websocket/handlers/VOICE_STATE_UPDATE.js:4:35)
2021-03-04T06:25:06.238632+00:00 app[worker.1]:     at WebSocketManager.handlePacket (/app/node_modules/discord.js/src/client/websocket/WebSocketManager.js:384:31)
2021-03-04T06:25:06.238633+00:00 app[worker.1]:     at WebSocketShard.onPacket (/app/node_modules/discord.js/src/client/websocket/WebSocketShard.js:444:22)
2021-03-04T06:25:06.238633+00:00 app[worker.1]:     at WebSocketShard.onMessage (/app/node_modules/discord.js/src/client/websocket/WebSocketShard.js:301:10)
2021-03-04T06:25:06.238634+00:00 app[worker.1]:     at WebSocket.onMessage (/app/node_modules/ws/lib/event-target.js:132:16)
2021-03-04T06:25:06.238634+00:00 app[worker.1]:     at WebSocket.emit (events.js:315:20)
2021-03-04T06:25:06.238634+00:00 app[worker.1]:     at Receiver.receiverOnMessage (/app/node_modules/ws/lib/websocket.js:825:20)
2021-03-04T06:25:06.279643+00:00 heroku[worker.1]: Process exited with status 1
2021-03-04T06:25:06.340294+00:00 heroku[worker.1]: State changed from up to crashed

The updated code:

const Discord = require('discord.js'),
    DisTube = require('distube'),
    client = new Discord.Client(),
    config = {
        prefix: "em!",
        token: process.env.TOKEN || "[insert discord bot token]"
    };


const distube = new DisTube(client, { searchSongs: true, emitNewSongOnly: true });

client.on('ready', () => {
    console.log(`e-Music is up and running`);
    client.user.setActivity(`em!play`)
});

client.on("message", async (message) => {
    if (message.author.bot) return;
    if (!message.content.startsWith(config.prefix)) return;
    const args = message.content.slice(config.prefix.length).trim().split(/ +/g);
    const command = args.shift();

    if (command == "play")
        distube.play(message, args.join(" "));

    if (["repeat", "loop"].includes(command))
        distube.setRepeatMode(message, parseInt(args[0]));

    if (command == "stop") {
        distube.stop(message);
        message.channel.send("Stopped the music!");
    }

    if (command == "skip")
        distube.skip(message);

    if (command == "queue") {
        let queue = distube.getQueue(message);
        message.channel.send('Current queue:\n' + queue.songs.map((song, id) =>
            `**${id + 1}**. ${song.name} - \`${song.formattedDuration}\``
        ).slice(0, 10).join("\n"));
    }

    if ([`3d`, `bassboost`, `echo`, `karaoke`, `nightcore`, `vaporwave`].includes(command)) {
        let filter = distube.setFilter(message, command);
        message.channel.send("Current queue filter: " + (filter || "Off"));
    }
});

client.on("voiceStateUpdate", (oldVoiceState, newVoiceState) => {
    if (newVoiceState.id == client.user.id) {
        connection.voice.setSelfDeaf(true);
    };
});

const status = (queue) => `Volume: \`${queue.volume}%\` | Filter: \`${queue.filter || "Off"}\` | Loop: \`${queue.repeatMode ? queue.repeatMode == 2 ? "All Queue" : "This Song" : "Off"}\` | Autoplay: \`${queue.autoplay ? "On" : "Off"}\``;

distube
    .on("playSong", (message, queue, song) => message.channel.send(
        `Playing \`${song.name}\` - \`${song.formattedDuration}\`\nRequested by: ${song.user}\n${status(queue)}`
    ))
    .on("addSong", (message, queue, song) => message.channel.send(
        `Added ${song.name} - \`${song.formattedDuration}\` to the queue by ${song.user}`
    ))
    .on("playList", (message, queue, playlist, song) => message.channel.send(
        `Play \`${playlist.name}\` playlist (${playlist.songs.length} songs).\nRequested by: ${song.user}\nNow playing \`${song.name}\` - \`${song.formattedDuration}\`\n${status(queue)}`
    ))
    .on("addList", (message, queue, playlist) => message.channel.send(
        `Added \`${playlist.name}\` playlist (${playlist.songs.length} songs) to queue\n${status(queue)}`
    ))

    .on("searchResult", (message, result) => {
        let i = 0;
        message.channel.send(`**Choose an option from below**\n${result.map(song => `**${++i}**. ${song.name} - \`${song.formattedDuration}\``).join("\n")}\n*Enter anything else or wait 60 seconds to cancel*`);
    })

    .on("searchCancel", (message) => message.channel.send(`Searching canceled`))
    .on("error", (message, e) => {
        console.error(e)
        message.channel.send("An error encountered: " + e);
    });

client.login(config.token);

Answer 1

If you read the error ReferenceError: connection is not defined, it tells you what is wrong. connection in the following code is not a variable:

client.on("voiceStateUpdate", (oldVoiceState, newVoiceState) => {
    if (newVoiceState.id == client.user.id) {
        connection.voice.setSelfDeaf(true);
    };
});

There is a connection property on newVoiceState though, although that isn't what you want in this scenario. You would want to use the .setSelfDeaf method from VoiceState:

client.on("voiceStateUpdate", (oldVoiceState, newVoiceState) => {
    if (newVoiceState.id == client.user.id) {
       newVoiceState.setSelfDeaf(true);
    };
});