const users = new Set();
<Client>.guilds.cache.forEach(guild => guild.members.cache.forEach(member => users.add(member.id)));

users.size

const users = new Set();
<Client>.guilds.cache.forEach(guild => guild.members.cache.forEach(member => users.add(member.id)));

users.size

<Client>.guilds.cache.map(x => x.members.cache).reduce((prev, current) => [...new Set([...prev, current])], []).length

<Client>.guilds.cache.map(x => x.members.cache).reduce((prev, current) => [...new Set([...prev, current])], []).length

if (<VoiceState>.channel.id === <Guild>.afkChannel.id) {
// ... 
}

if (<VoiceState>.channel.id === <Guild>.afkChannel.id) {
// ... 
}