bolt-app-mention.js

// https://github.com/slackapi/bolt/blob/43b8b78042752778484edd6018a37464bbfae2f5/src/middleware/builtin.ts#L208-L23
function matchText(pattern) {
  return async ({ event, context, next }) => {
    let tempMatches

    if (event.text === undefined) {
      return
    }

    // Filter out messages that don't contain the pattern
    if (typeof pattern === "string") {
      if (!event.text.includes(pattern)) {
        return
      }
    } else {
      tempMatches = event.text.match(pattern)

      if (tempMatches !== null) {
        context["matches"] = tempMatches
      } else {
        return
      }
    }

    await next()
  }
}

app.event("app_mention", matchText("ping"), async ({ event, say }) => {
  // do stuff
})