events.js

const { createEventAdapter } = require('@slack/events-api')
const slackSigningSecret = process.env.SLACK_SIGNING_SECRET
const slackEvents = createEventAdapter(slackSigningSecret)

function listenForEvents(app) {
  app.use('/events', slackEvents.requestListener())
}

slackEvents.on('app_mention', (event) => {
  console.log(`Received an app_mention event from user ${event.user} in channel ${event.channel}`)
})

// All errors in listeners are caught here. If this weren't caught, the program would terminate.
slackEvents.on('error', (error) => {
  console.log(`error: ${error}`)
})

module.exports.listenForEvents = listenForEvents