Discord - Ratelimiting made easy

example.ts

import { Bucket } from './ratelimiting';
import { User } from 'discord.js';

// Create your ratelimit bucket here. This is where we'll be storing everyone who uses a command.
const ratelimitBucket = new Bucket<User>(/* enter your timeout here in milliseconds. */ 5000);

// This obviously won't work, but you need to enter this code (or your variant) into your command handler.
onCommand((message: Message) => {
  // Enter the member into the bucket, so we can keep track of them. If the user is already in the bucket, this does nothing.
  this.enterMember(message.author);
  
  if (ratelimitBucket.check(message.author)) {
    reply(`You need to wait ${ratelimitBucket.remaining(message.author)} ms before you use another command.`);
    return;
  }
  
  // Otherwise, the user is good to go.
});

ratelimiting.ts

interface QueueMember<MemberType> {
  member: MemberType;
  end: number;
}

export class Bucket<MemberType> {
  private readonly queue: QueueMember<MemberType>[] = [];
  public constructor(public timeout: number) { }

  public has(member: MemberType): boolean {
    return this.queue.some(x => x.member === member);
  }

  public enterMember(member: MemberType): void {
    if (this.has(member)) {
      return;
    }

    const end = Date.now() + this.timeout;
    this.push(member, end);
  }

  public check(member: MemberType): boolean {
    const queueMember = this.findQueueMember(member);

    if (!queueMember) {
      // That member isn't currently in the queue. Return false to signal that they're allowed.
      return false;
    }

    // The member does exist, and we need to check if they can pass.
    const { end } = queueMember;
    const hasElapsed = Date.now() > end;

    if (hasElapsed) {
      this.removeMember(member);
    }

    return hasElapsed;
  }

  public remaining(member: MemberType): number | void {
    const queueMember = this.findQueueMember(member);

    if (queueMember) {
      return queueMember.end;
    }
  }

  protected removeMember(member: MemberType): void {
    const index = this.queue.findIndex(x => x.member === member);

    if (index !== -1) {
      // The member is present in the queue. Remove it.
      this.queue.splice(index, 1);
    }
  }

  protected push(member: MemberType, end: number): void {
    this.queue.push({
      member,
      end
    });
  }

  protected findQueueMember(member: MemberType): void | QueueMember<MemberType> {
    return this.queue.find(x => x.member === member);
  }
}