Deletes slack public/private channel and chat messages.

delete-slack-messages.js

#!/usr/bin/env node

// Channel ID is on the the browser URL.: https://mycompany.slack.com/messages/MYCHANNELID/
// Pass it as a parameter: node ./delete-slack-messages.js CHANNEL_ID

// CONFIGURATION #######################################################################################################

const token = '<token>'; // You can learn it from: https://api.slack.com/custom-integrations/legacy-tokens

// GLOBALS #############################################################################################################

let channel = '';

if (process.argv[0].indexOf('node') !== -1 && process.argv.length > 2) {
  channel = process.argv[2];
} else if (process.argv[0].indexOf('delete') !== -1 && process.argv.length > 1) {
  channel = process.argv[1];
} else {
  console.log('Usage: node ./delete-slack-messages.js CHANNEL_ID');
  process.exit(1);
}

const https         = require('https');
const baseApiUrl    = 'https://slack.com/api/';
const messages      = [];
const historyApiUrl = baseApiUrl + 'conversations.history?token=' + token + '&count=1000&channel=' + channel + '&cursor=';
const deleteApiUrl  = baseApiUrl + 'chat.delete?token=' + token + '&channel=' + channel + '&ts='
let   delay         = 300; // Delay between delete operations in milliseconds
let   nextCursor    = '';

// ---------------------------------------------------------------------------------------------------------------------

function deleteMessage() {

  if (messages.length == 0) {

    if (nextCursor) {
      processHistory();
    }

    return;
  }

  const ts = messages.shift();

  https.get(deleteApiUrl + ts, function (res) {

    let body = '';

    res.on('data', function (chunk) {
      body += chunk;
    });

    res.on('end', function(){
      const response = JSON.parse(body);

      if (response.ok === true) {
        console.log(ts + ' deleted!');
      } else if (response.ok === false) {
        console.log(ts + ' could not be deleted! (' + response.error + ')');

        if (response.error === 'ratelimited') {
          delay += 100; // If rate limited error caught then we need to increase delay.
          messages.push(ts);
        }
      }

      setTimeout(deleteMessage, delay);
    });
  }).on('error', function (e) {
    console.error("Got an error: ", e);
  });
}

// ---------------------------------------------------------------------------------------------------------------------

function processHistory() {

  https.get(historyApiUrl + nextCursor, function(res) {

    let body = '';

    res.on('data', function (chunk) {
      body += chunk;
    });

    res.on('end', function () {

      nextCursor = null;

      const response = JSON.parse(body);

      if (response.ok) {
        if (response.messages && response.messages.length > 0) {

          if (response.has_more) {
            nextCursor = response.response_metadata.next_cursor;
          }

          for (let i = 0; i < response.messages.length; i++) {
            messages.push(response.messages[i].ts);
          }

          deleteMessage();
        }
      } else {
        throw new Error(response.error)
      }
    });
  }).on('error', function (e) {
    console.error("Got an error: ", e);
  });
}

// ---------------------------------------------------------------------------------------------------------------------

processHistory();