Listening to messages

To listen to messages that your app has access to receive, you can use the message() method which filters out events that aren’t of type message. A message() listener is equivalent to event('message').

The message() listener accepts an optional pattern parameter of type string or RegExp object which filters out any messages that don’t match the pattern.

// This will match any message that contains 👋
app.message(':wave:', async ({ message, say }) => {
  // Handle only newly posted messages here
  if (message.subtype === undefined
    || message.subtype === 'bot_message'
    || message.subtype === 'file_share'
    || message.subtype === 'thread_broadcast') {
    await say(`Hello, <@${message.user}>`);
  }
});

Using a RegExp pattern

A RegExp pattern can be used instead of a string for more granular matching.

All of the results of the RegExp match will be in context.matches.

app.message(/^(hi|hello|hey).*/, async ({ context, say }) => {
  // RegExp matches are inside of context.matches
  const greeting = context.matches[0];

  await say(`${greeting}, how are you?`);
});

Filtering on event subtypes

You can filter on subtypes of events by using the built-in subtype() middleware. Common message subtypes like message_changed and message_replied can be found on the message event page.

// Import subtype from the package
const { App, subtype } = require('@slack/bolt');

// Matches all message changes from users
app.message(subtype('message_changed'), ({ event, logger }) => {
  // This if statement is required in TypeScript code
  if (event.subtype === 'message_changed'
    && !event.message.subtype
    && !event.previous_message.subtype) {
    logger.info(`The user ${event.message.user} changed their message from ${event.previous_message.text} to ${event.message.text}`);
  }
});