Slack OAuth

Connect Slack to send messages, read channels, and manage files.

JsWorkflows provides a platform-managed Slack OAuth app. You do not need to create your own Slack app or manage client credentials.

Available scopes

 |  Resource  |  Operation  |  Scope  |

 |  Messaging  |  Send message  |  chat:write, users:read  |
 |  Messaging  |  Read messages  |  channels:history, groups:history, im:history, mpim:history  |
 |  Users  |  Get user info / list users  |  users:read  |
 |  Channels  |  List channels  |  channels:read  |
 |  Channels  |  Join channel  |  channels:join  |
 |  Files  |  Upload file  |  files:write  |
 |  Files  |  Read files  |  files:read  |
 |  Reactions  |  Add/read reactions  |  reactions:write, reactions:read  |

Example: post a message

export class Workflow {
  async start(data, headers, api) {
    const { token, error } = await api.getOAuthToken('my-slack');
    if (error  |  |  !token) throw new Error(error  |  |  'Missing Slack token');

    const response = await fetch('https://slack.com/api/chat.postMessage', {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json; charset=utf-8',
        Authorization: Bearer ${token},
      },
      body: JSON.stringify({
        channel: 'C0123456789',
        text: New order #${data.ordernumber}: ${data.totalprice} ${data.currency},
        blocks: [
          {
            type: 'section',
            text: {
              type: 'mrkdwn',
              text: New order #${data.ordernumber}: ${data.totalprice} ${data.currency},
            },
          },
        ],
      }),
    });

    if (!response.ok) {
      throw new Error(Slack HTTP ${response.status}: ${await response.text()});
    }

    const result = await response.json();
    if (!result.ok) {
      throw new Error(Slack API error: ${result.error  |  |  'unknownerror'});
    }
  }
}

Use a channel ID when possible. It is the safest value to store in workflow config and pass to Slack APIs.

Example: upload a file

Slack's current upload flow is:

1. call files.getUploadURLExternal
2. upload the file bytes to the returned uploadurl
3. call files.completeUploadExternal

const { token, error } = await api.getOAuthToken('my-slack');
if (error  |  |  !token) throw new Error(error  |  |  'Missing Slack token');

const csvString = 'sku,available\\nABC-123,42\\n';
const fileBytes = new TextEncoder().encode(csvString);

const initResponse = await fetch('https://slack.com/api/files.getUploadURLExternal', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json; charset=utf-8',
    Authorization: Bearer ${token},
  },
  body: JSON.stringify({
    filename: 'report.csv',
    length: fileBytes.byteLength,
  }),
});

if (!initResponse.ok) {
  throw new Error(Slack HTTP ${initResponse.status}: ${await initResponse.text()});
}

const initResult = await initResponse.json();
if (!initResult.ok) {
  throw new Error(Slack API error: ${initResult.error  |  |  'unknownerror'});
}

const uploadResponse = await fetch(initResult.uploadurl, {
  method: 'POST',
  headers: { 'Content-Type': 'text/csv; charset=utf-8' },
  body: fileBytes,
});

if (!uploadResponse.ok) {
  throw new Error(Slack upload failed: ${uploadResponse.status} ${await uploadResponse.text()});
}

const completeResponse = await fetch('https://slack.com/api/files.completeUploadExternal', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json; charset=utf-8',
    Authorization: Bearer ${token},
  },
  body: JSON.stringify({
    files: [{ id: initResult.fileid, title: 'report.csv' }],
    channelid: 'C0123456789',
    initialcomment: 'Daily inventory report',
  }),
});

if (!completeResponse.ok) {
  throw new Error(Slack HTTP ${completeResponse.status}: ${await completeResponse.text()});
}

const completeResult = await completeResponse.json();
if (!completeResult.ok) {
  throw new Error(Slack API error: ${completeResult.error  |  |  'unknownerror'});
}

For file sharing, use channelid or channels with Slack IDs. Do not use #channel-name in the file upload completion request.