firebase-functions-universal.js

// ... pass this to Express or firebase functions.https.onRequest:
function universal(req, res) {
    renderModuleFactory(AppServerModuleNgFactory, {
        document: index,
        url: req.path || '/',
        extraProviders: [
            { provide: 'firebaseAdmin', useValue: admin }
        ]
    })
        .then(function (html) {
            res.send(html);
        }).catch(function (e) {
            console.log(e)
        });
}