import * as functions from 'firebase-functions'; import * as express from 'express'; const app = express(); app.get('/events/:id', (request, response) => { const userAgent = request.get('user-agent'); if (userAgent.indexOf("facebookexternalhit") === 0) { res.status(200).send(` Facebook `); } }); exports.eventsReqHandler = functions.https.onRequest(app);