discord.js/src/structures/DMChannel.js

const User = require('./User');
const Channel = require('./Channel');
const TextBasedChannel = require('./interface/TextBasedChannel');
const Collection = require('../util/Collection');

/**
 * Represents a Direct Message Channel between two users.
 * @extends {Channel}
 * @implements {TextBasedChannel}
 */
class DMChannel extends Channel {
  constructor(client, data) {
    super(client, data);
    this.messages = new Collection();
  }

  setup(data) {
    super.setup(data);

    /**
     * The recipient on the other end of the DM
     * @type {User}
     */
    this.recipient = this.client.users.get(data.recipients[0].id) || new User(this.client, data.recipients[0]);

    this.type = 'dm';
    this.lastMessageID = data.last_message_id;
    this._typing = new Map();
  }

  /**
   * When concatenated with a string, this automatically concatenates the recipient's mention instead of the
   * DM channel object.
   * @returns {string}
   */
  toString() {
    return this.recipient.toString();
  }

  // These are here only for documentation purposes - they are implemented by TextBasedChannel
  sendMessage() { return; }
  sendTTSMessage() { return; }
  sendFile() { return; }
  fetchMessage() { return; }
  fetchMessages() { return; }
  fetchPinnedMessages() { return; }
  startTyping() { return; }
  stopTyping() { return; }
  get typing() { return; }
  get typingCount() { return; }
  createCollector() { return; }
  awaitMessages() { return; }
  bulkDelete() { return; }
  _cacheMessage() { return; }
}

TextBasedChannel.applyToClass(DMChannel, true);

module.exports = DMChannel;