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Webhook

The @slack/webhook package contains a helper for making requests to Slack's Incoming Webhooks or Workflow Builder. Use it in your app to send a notification to a channel or start a workflow.

Installation​

$ npm install @slack/webhook

Initialize the webhook​

The package exports a IncomingWebhook class. You'll need to initialize it with the URL you received from Slack.

The URL can come from installation in your development workspace, which is shown in the app configuration pages. Or, the URL could be in the response from oauth.v2.access when the app is distributed and installed into another workspace.

const { IncomingWebhook } = require('@slack/webhook');

// Read a url from the environment variables
const url = process.env.SLACK_WEBHOOK_URL;

// Initialize
const webhook = new IncomingWebhook(url);

Setting default arguments

The webhook can be initialized with default arguments that are reused each time a notification is sent. Use the second parameter to the constructor to set the default arguments.

const { IncomingWebhook } = require('@slack/webhook');
const url = process.env.SLACK_WEBHOOK_URL;

// Initialize with defaults
const webhook = new IncomingWebhook(url, {
  icon_emoji: ':bowtie:',
});

Send a notification​

Something interesting just happened in your app, so it's time to send the notification! Call the .send(options) method on the webhook. The options parameter is an object that should describe the contents of the message. The method returns a Promise that resolves once the notification is sent.

const { IncomingWebhook } = require('@slack/webhook');
const url = process.env.SLACK_WEBHOOK_URL;

const webhook = new IncomingWebhook(url);

// Send the notification
(async () => {
  await webhook.send({
    text: 'I\'ve got news for you...',
  });
})();

Trigger a Workflow Builder workflow​

The package also exports a WebhookTrigger class for Workflow Builder webhook triggers which accepts an optional, flattened, stringified JSON payload sent to start a workflow.

const { WebhookTrigger } = require('@slack/webhook');
const url = process.env.SLACK_WEBHOOK_TRIGGER_URL;

const trigger = new WebhookTrigger(url);

(async () => {
  // Keys should match the variables your workflow expects
  await trigger.send({
    customer_name: 'Ada Lovelace',
    order_id: '1024',
  });
})();

Retry failed requests​

Both IncomingWebhook and WebhookTrigger classes can retry failed requests. Retries are off by default; pass a retryConfig to opt in. The package re-exports the same named policies as @slack/web-api on retryPolicies, or you can supply your own retry options.

const { IncomingWebhook, retryPolicies } = require('@slack/webhook');
const url = process.env.SLACK_WEBHOOK_URL;

const webhook = new IncomingWebhook(url, {
  retryConfig: retryPolicies.fiveRetriesInFiveMinutes,
});

Only transient failures are retried: server errors (5xx) and network errors with no response. Client errors (4xx), including rate limits (429), fail immediately without a retry.

Proxy requests with a custom agent​

The webhook allows you to customize the HTTP Agent used to create the connection to Slack. Using this option is the best way to make all requests from your app through a proxy, which is a common requirement in many corporate settings.

In order to create an Agent from some proxy information (such as a host, port, username, and password), you can use one of many npm packages. We recommend https-proxy-agent. Start by installing this package and saving it to your package.json.

$ npm install https-proxy-agent

Import the HttpsProxyAgent class, and create an instance that can be used as the agent option of the IncomingWebhook.

const { IncomingWebhook } = require('@slack/webhook');
const HttpsProxyAgent = require('https-proxy-agent');
const url = process.env.SLACK_WEBHOOK_URL;

// One of the ways you can configure HttpsProxyAgent is using a simple string.
// See: https://github.com/TooTallNate/node-https-proxy-agent for more options
const proxy = new HttpsProxyAgent(process.env.http_proxy || 'http://168.63.76.32:3128');

// Initialize with the proxy agent option
const webhook = new IncomingWebhook(token, { agent: proxy });

// Sending this webhook will now go through the proxy
(async () => {
  await webhook.send({
    text: 'I\'ve got news for you...',
  });
})();