channel.fetchMessages({ limit: numberOfMessages }).then((messages: Collection<string, Message>) => {
   messages.forEach((message: Message) => {
     message.delete()
   })
   channel.send(`Pruning ${numberOfMessages - 1} messages!`)
     .then((reply: Message) => {
       reply.delete(3000)
     }
   )
 })

function pickN(users: Collection<string, GuildMember>, n: number): string {
    const guildMembers = users.array().filter(member => !member.user.bot && member.user.presence.status === "online");

    if (guildMembers.length === 0)
        return `There are no users in the specified channel.`;
    else if (n > guildMembers.length)
        return guildMembers.map(member => ` - ${member.displayName}#${member.user.discriminator}`).join("\n");
    else {
        // Taken from https://jsperf.com/k-random-elements-from-array/2
        let result: GuildMember[] = new Array(n);
        let taken = new Array(n);
        let len = guildMembers.length;

        while (n--) {
            const randNum = Math.floor(Math.random() * len);
            console.log(`RAND: ${randNum}`);
            const toAdd = guildMembers[randNum];
            result[n] = guildMembers[randNum in taken ? taken[randNum] : randNum];
            taken[randNum] = --len;
        }

        return result.map(member => ` - ${member.displayName}#${member.user.discriminator}`).join("\n");
    }
}

	public postCheck(reaction: MessageReaction, user: User): string {
		this.users.set(user.id, user);
		if (this.options.max && ++this.total >= this.options.max) { return 'limit'; }
		if (this.options.maxEmojis && this.collected.size >= this.options.maxEmojis) { return 'emojiLimit'; }
		if (this.options.maxUsers && this.users.size >= this.options.maxUsers) { return 'userLimit'; }
		return null;
	}