Slack API: Get User details based on reactions

index.js

require('dotenv').config();
const { App } = require('@slack/bolt');

const reaction = process.env.EMOJI;
const url = process.env.URL;

const app = new App({
  signingSecret: process.env.SLACK_SIGNING_SECRET,
  token: process.env.SLACK_BOT_TOKEN,
});

const findChannelIdAndTimestamp = (url) => {
  const [channel, timestamp] = url.split('/').pop().split('-');
  return { channel, timestamp };
};

const { channel, timestamp } = findChannelIdAndTimestamp(url);

if (!url.includes('/thread') || !channel || !timestamp) {
  throw Error('Unable to parse Slack Thread URL.');
}

const getReactions = async (channel, timestamp) => {
  const convos = await app.client.conversations.info({
    channel,
  });

  const {
    channel: { name, is_channel, is_member },
  } = convos;

  if (!is_channel) {
    throw Error('Please provide a valid URL to a Slack Channel');
  }

  if (!is_member) {
    await app.client.conversations.join({
      channel,
    });
  }

  const {
    message: { text, reactions },
  } = await app.client.reactions.get({
    channel,
    timestamp,
    full: true,
  });

  const reactionUsers = reactions.find((r) => r.name === reaction)?.users;

  var users = await Promise.all(
    reactionUsers.map(async (user) => {
      const {
        user: {
          name,
          real_name,
          profile: { email },
        },
      } = await app.client.users.info({
        user,
      });

      return {
        name,
        real_name,
        email,
      };
    })
  );

  const output = { channel: name, message: text, reaction, users };
  console.log(`
Users reacted with :${output.reaction}: are:  

${output.users.map((user) => `${user.real_name};${user.email}`).join('\n')}
  `);
};

(async () => {
  await app.start(process.env.PORT || 3000);
  console.log('⚡️ Bolted. Looking for ' + channel);
  await getReactions(channel, timestamp);
})();

How to use

Setup OAuth Scope

Set up a slack app with the following OAuth Scope:

• channels:join
• channels:read
• chat:write
• users:read
• users:read.email

Get channel and timestamp

• Get the Bot User OAuth Token from OAuth & Permissions and Signing Secret from App Credentials.
• Find the thread in slack and copy the URL (ensure the URL includes /threads).
• Type the EMOJI you want to get reaction user details for.

Fill in the .env with the information:

SLACK_SIGNING_SECRET=123abc...
SLACK_BOT_TOKEN=xoxb-...
URL=https://app.slack.com/client/T124ABC32/C12ABCDEF/thread/C12ABCDEF-1631693056.014500
EMOJI=italian-chef-gusto

Run in console

• Run npm init y && npm install @slack/bolt dotenv
• Run node index.js