Get users (and their email, first name and last name) from Slack channel

README.md

Usage

1. You need to create a new Slack app with following scopes:

   • channels:read
   • groups:read
   • users:read
   • users:read.email

2. Install it into a workspace

3. Invite it into a channel: /invite @<app-name>

4. Install npm i @slack/web-api

5. Run the script (NodeJS v20+ required):

   export SLACK_TOKEN=<apps-bot-token> ./slack-channel-users.mjs --channel="<channel-id>"

slack-channel-users.mjs

#!/usr/bin/env node
import { parseArgs } from "node:util";
import assert from "node:assert/strict";
import { WebClient } from "@slack/web-api";

const token = process.env.SLACK_TOKEN;
assert(typeof token === "string", "SLACK_TOKEN missing");
const web = new WebClient(token);

/**
 * Reads channel ID from `--channel` CLI option
 * @returns {string}
 */
function getChannelFromArgs() {
  const args = parseArgs({ options: { channel: { type: "string" } } });
  assert(
    typeof args.values.channel === "string",
    "Channel CLI option is required"
  );
  return args.values.channel;
}

/**
 * Asserts that the response is a valid ConversationsMembers
 * @param {unknown} value
 * @returns {asserts value is import("@slack/web-api").ConversationsMembersResponse}
 */
function assertMembersResponse(value) {
  assert(value.ok, "API request failed");
  assert(Array.isArray(value.members), "Members not found");
}

/**
 * Get members of a channel
 * @param {string} channel
 * @returns {Promise<string[]>} list of member IDs
 */
async function getMembers(channel) {
  /** @type {string[]} */
  const members = [];

  for await (const page of web.paginate("conversations.members", { channel })) {
    assert(page.ok, "API request failed");
    assert(Array.isArray(page.members), "Members not found");
    members.push(...page.members);
  }
  return members;
}

/**
 * Get single user
 * @param {string} user
 * @returns {Promise<Exclude<import("@slack/web-api").UsersInfoResponse["user"], undefined>>}
 */
async function getUser(user) {
  const response = await web.users.info({ user });
  assert(response.ok, "API request failed");
  assert(typeof response.user !== "undefined", "User not found");
  return response.user;
}

/**
 * Describe user basic data
 * @typedef {Object} UserBasicData
 * @prop {string} email
 * @prop {string} firstName
 * @prop {string} lastName
 */

/**
 * Parse User object from UsersInfoResponse
 * @param {Exclude<import("@slack/web-api").UsersInfoResponse["user"], undefined>} user
 * @returns {UserBasicData}
 */
function parseUserBasicData(user) {
  assert(typeof user.profile !== "undefined", "Profile not found");
  const { profile } = user;
  return {
    email: profile.email,
    firstName: profile.first_name,
    lastName: profile.last_name,
  };
}

/**
 * Main workflow
 * @param {string} channelId
 */
async function main(channelId) {
  const members = await getMembers(channelId);
  const users = await Promise.all(members.map((member) => getUser(member)));
  const usersBasicData = users.map(parseUserBasicData);
  console.log(usersBasicData);
}

main(getChannelFromArgs()).catch(console.error);