很简单，试试这个：

// If the bot is not connected to a voice channel, the 'channel' object should be 'undefined'
if(msg.guild.voice.cannel)
  {
    msg.channel.send(`I'm in a voice channel!`);
  }
else
  {
    console.log(`I'm not in a voice channel!`);
  }

注：

这只检查message的channel，而不是如果bot连接到服务器上的任何voice channel!
如果您要检查，如果他连接到任何voice channel，您应该检查Viriatos answer

编辑：

您还可以将Vitiaro's answer缩减为一行：

msg.guild.channels.cache.some(channel => (channel.type === 'voice' && channel.members.has(Client.user.id)) ? msg.channel.send('It is on a voice channel') : msg.channel.send('It is not on a voice channel')

但你必须自己决定这是否更清楚。

参考文献：

• Similar StackOverflow question
• guild#voice#channel

如果我没理解错的话，你想查看bot是否在msg.guild对应的公会的任意语音通道中：

if(msg.guild.channels.cache.some(channel => (channel.type === 'voice' && channel.members.has(Client.user.id)) {
    msg.channel.send('It is on a voice channel'); // Replies on the same channel the command was sent to
}
else {
    msg.channel.send('It is not on a voice channel');
}

以下是最新discord.js版本（v14）的解决方案

if(interaction.guild.members.me.voice.channel){
   console.log("I am connected to a Voice Channel!")
}