I did something similar in a project not too long ago where I had to mute everyone but the person issuing the command.

You can accomplish this by iterating through an array of all users in the current channel.

// Your invokation here, for example your switch/case hook for some command (i.e. '!muteall')

// Check if user is in a voice channel:

if (message.member.voice.channel) {

  let channel = message.guild.channels.cache.get(message.member.voice.channel.id);

  for (const [memberID, member] of channel.members) {

    // I added the following if statement to mute everyone but the invoker:

    // if (member != message.member)



    // This single line however, nested inside the for loop, should mute everyone in the channel:

    member.voice.setMute(true);

  }

} else {

  message.reply('You need to join a voice channel first!');

}