example_slack_message_handler.js

// Initialize using signing secret from environment variables
const { createEventAdapter } = require('@slack/events-api');
const slackEvents = createEventAdapter(process.env.SLACK_SIGNING_SECRET);
const port = process.env.PORT || 3000;

// Attach listeners to events by Slack Event "type". See: https://api.slack.com/events/message.im
slackEvents.on('message', (event) => {
  console.log(`Received a message event: user ${event.user} in channel ${event.channel} says ${event.text}`);
});