Firestore database not connecting with Firebase cloud functions

Question

I am trying to retrieve Firestore database information through Express.js used in Firebase cloud functions. My index.js files inside the function folder look like:

const functions = require('firebase-functions');
const admin = require("firebase-admin");
const db = admin.firestore();
admin.initializeApp();
const express = require('express');
const app= express();

app.get("/teacher/:uid",function(req,res){
    const id = req.params.uid;
    const doc = db.collection('users').doc(id).get();
    res.send(doc);
    //res.render("teacher",{id : id});
})

the script part of my index.html file looks like:

<body>

// some html code 
<!---script follow-->
<script src="https://code.jquery.com/jquery-3.4.1.slim.min.js" integrity="sha384-J6qa4849blE2+poT4WnyKhv5vZF5SrPo0iEjwBvKU7imGFAV0wwj1yYfoRSJoZ+n" crossorigin="anonymous"></script>
<script src="https://cdn.jsdelivr.net/npm/[email protected]/dist/umd/popper.min.js" integrity="sha384-Q6E9RHvbIyZFJoft+2mJbHaEWldlvI9IOYy5n3zV9zzTtmI3UksdQRVvoxMfooAo" crossorigin="anonymous"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/js/bootstrap.min.js" integrity="sha384-wfSDF2E50Y2D1uUdj0O3uMBJnjuUD4Ih7YwaYd1iqfktj0Uod8GCExl3Og8ifwB6" crossorigin="anonymous"></script>
<script src="https://www.gstatic.com/firebasejs/7.14.2/firebase-app.js"></script>
<script src="https://www.gstatic.com/firebasejs/7.14.2/firebase-auth.js"></script>
<script src="https://www.gstatic.com/firebasejs/7.14.2/firebase-firestore.js"></script>
<script src="https://www.gstatic.com/firebasejs/7.14.2/firebase-functions.js"></script>
<script>
  // web app's Firebase configuration
  var firebaseConfig = {
    apiKey: "xyz",
    authDomain: "xyz",
    databaseURL: "xyz",
    projectId: "xyz",
    appId: "xyz"
  };
  // i have replaced the actual keys and urls with xyz

  firebase.initializeApp(firebaseConfig);
  const auth= firebase.auth();
  const db= firebase.firestore();
  const functions = firebase.functions();

</script>

<script src="auth.js"></script>
</body>

ERROR : 
on command firebase serve --only functions , i am getting this error 

 Error: The default Firebase app does not exist. Make sure you call initializeApp() before using any of the Firebase services.
    at FirebaseAppError.FirebaseError [as constructor] (/home/chahat/Desktop/firebase/functions/node_modules/firebase-admin/lib/utils/error.js:42:28)
    at FirebaseAppError.PrefixedFirebaseError [as constructor] (/home/chahat/Desktop/firebase/functions/node_modules/firebase-admin/lib/utils/error.js:88:28)
    at new FirebaseAppError (/home/chahat/Desktop/firebase/functions/node_modules/firebase-admin/lib/utils/error.js:123:28)
    at FirebaseNamespaceInternals.app (/home/chahat/Desktop/firebase/functions/node_modules/firebase-admin/lib/firebase-namespace.js:101:19)
    at FirebaseNamespace.app (/home/chahat/Desktop/firebase/functions/node_modules/firebase-admin/lib/firebase-namespace.js:452:30)
    at FirebaseNamespace.ensureApp (/home/chahat/Desktop/firebase/functions/node_modules/firebase-admin/lib/firebase-namespace.js:468:24)
    at Proxy.fn (/home/chahat/Desktop/firebase/functions/node_modules/firebase-admin/lib/firebase-namespace.js:327:30)
    at Object.<anonymous> (/home/chahat/Desktop/firebase/functions/index.js:3:18)
    at Module._compile (internal/modules/cjs/loader.js:1156:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1176:10)
⚠  We were unable to load your functions code. (see above)

Renaud Tarnec Renaud Tarnec · Accepted Answer · 2020-05-07T08:14:36

There are several parts that you should change in your Cloud Function code:

 const functions = require('firebase-functions');
 const admin = require("firebase-admin");
 admin.initializeApp();

 const db = admin.firestore();   //#1

 const express = require('express');
 const app= express();

 app.get("/teacher/:uid",function(req, res){
    const id = req.params.uid;
    db.collection('users').doc(id).get()   //#2  
    .then(snap => {
        res.send(snap.data());
    })
    .catch(error => {...})
 })

Define Firestore as admin.firestore() after having initialized the Admin SDK.
The get() method is asynchronous. You need to wait for the Promise its returns to resolve before being able to return the response. More details in the doc: https://firebase.google.com/docs/firestore/query-data/get-data#get_a_document and https://firebase.google.com/docs/functions/video-series

Firestore database not connecting with Firebase cloud functions

1 Answers