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if(!message.member.voice.channel) return message.channel.send("Please connect to a voice channel!"); //If you are not in the voice channel, then return a message
message.member.voice.channel.join(); //Join the voice channel
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const VCchannelID = ('id');
const VCchannel = guild.channels.cache.get(VCchannelID);
VCchannel.join();