Firebase cloud function for firestore

index.js

const functions = require('firebase-functions');
const admin = require('firebase-admin');
// var serviceAccount = require("/home/bmabir/dev/tran-dao-8e837f43806d.json");
admin.initializeApp({
    credential: admin.credential.applicationDefault()
});
const db = admin.firestore();
// // Create and Deploy Your First Cloud Functions
// // https://firebase.google.com/docs/functions/write-firebase-functions
//
exports.helloWorld = functions.https.onRequest((request, response) => {
 response.send("Hello from tran dao server!");
});

exports.get_relief = functions.https.onRequest((request, response) => {
    const docRef = db.collection('relief');
    docRef.get()
    .then(snapshot => {
        let arrayR = snapshot.docs.map(doc => {
            return doc.data();
        }); 
        return response.json(arrayR);        
    }).catch(err => {
        console.log('Error getting document', err);
      })
});