GramJS

const { Api, TelegramClient } = require("telegram");
const { StringSession } = require("telegram/sessions");

const session = new StringSession(""); // You should put your string session here
const client = new TelegramClient(session, apiId, apiHash, {});

(async function run() {
  await client.connect(); // This assumes you have already authenticated with .start()

  const result = await client.invoke(
    new Api.updates.GetChannelDifference({
      channel: "username",
      filter: new Api.ChannelMessagesFilter({
        ranges: [
          new Api.MessageRange({
            minId: 0,
            maxId: 0,
          }),
        ],
        excludeNewMessages: true,
      }),
      pts: 43,
      limit: 100,
      force: true,
    })
  );
  console.log(result); // prints the result
})();

import { Api, TelegramClient } from "telegram";
import { StringSession } from "telegram/sessions";

const session = new StringSession(""); // You should put your string session here
const client = new TelegramClient(session, apiId, apiHash, {});

(async function run() {
  await client.connect(); // This assumes you have already authenticated with .start()

  const result: Api.updates.ChannelDifference = await client.invoke(
    new Api.updates.GetChannelDifference({
      channel: "username",
      filter: new Api.ChannelMessagesFilter({
        ranges: [
          new Api.MessageRange({
            minId: 0,
            maxId: 0,
          }),
        ],
        excludeNewMessages: true,
      }),
      pts: 43,
      limit: 100,
      force: true,
    })
  );
  console.log(result); // prints the result
})();