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/
// Token can get from: https://api.slack.com/custom-integrations/legacy-tokens
// Pass it as a parameter: node ./delete-slack-messages.js TOKEN CHANNEL_ID
// Or use it without download the script: curl -Ls RAW_GIST_URL | node - TOKEN CHANNEL_ID

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

const [, , token, channel, _delay = 300] = process.argv
let delay = _delay // Allow inscrease delay later - thanks `colinricardo` for pointing it out

if (!token || !channel) {
  console.log('Usage: node ./delete-slack-messages.js TOKEN CHANNEL_ID')
  console.log('Usage: curl -Ls RAW_GIST_URL | node - TOKEN CHANNEL_ID')
  process.exit(1)
}

const https = require('https')
const baseApiUrl = 'https://slack.com/api'
const historyApiUrl = `${baseApiUrl}/conversations.history?token=${token}&count=1000&channel=${channel}&cursor=`
const deleteApiUrl = `${baseApiUrl}/chat.delete?token=${token}&channel=${channel}&ts=`

// ---------------------------------------------------------------------------------------------------------------------
const sleep = ms => new Promise(r => setTimeout(r, +ms))

const getJsonAsync = url =>
  new Promise((resolve, reject) =>
    https
      .get(url, res => {
        let body = ''

        res.on('data', chunk => (body += chunk))
        res.on('end', () => resolve(JSON.parse(body)))
      })
      .on('error', reject)
  )

async function deleteMessage(messages) {
  console.log(`Deleting ${messages.length} messages`)

  while (messages.length > 0) {
    const ts = messages.shift()
    const response = await getJsonAsync(deleteApiUrl + ts)

    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') {
        await sleep(1000)
        delay += 100 // If rate limited error caught then we need to increase delay.
        messages.unshift(ts)
      }
    }

    await sleep(delay)
  }
}

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

async function processHistory() {
  let nextCursor = ''
  while (true) {
    const { ok, error, messages, has_more, response_metadata } = await getJsonAsync(historyApiUrl + nextCursor)
    if (!ok) throw new Error(error)

    if (Array.isArray(messages)) await deleteMessage(messages.map(z => z.ts))
    else console.log('No message found')

    if (!has_more) break
    nextCursor = response_metadata.next_cursor
  }
}

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

processHistory().catch(console.log)

getJsonAsync and sleep async modifiers seem redundant. Generally, I avoid single line "if blocks".

Yeah, you're correct, those async modifier is redundant. Thank for pointing that out, I'll fix them right away.
Single line if block help make the code smaller and cleaner for me, but yes, it's personal opinion so please don't mind them 🙂

Update:
You can now use the gist without downloading it (using cURL and make node execute script from stdin)

curl -Ls RAW_GIST_URL | node - TOKEN CHANNEL_ID

One thing here: if you get rate limited, then the script tries to reassign the delay variable, which is a const, so the script fails.

Something like the following will fix it:

Change:

const [, , token, channel, delay = 300] = process.argv

to:

const [, , token, channel] = process.argv
let delay = 300;

Yeah you're right, thanks for pointing it out @colinricardo 👍

Gist updated 😄