firebase.js

const admin = require('firebase-admin');

var serviceAccount = require('path/to/serviceAccountKey.json');

admin.initializeApp({
    credential: admin.credential.cert(serviceAccount)
});

db.collection('locations').get()
    .then((snapshot) => {
        snapshot.forEach((doc) => {
            console.log(doc.id, '=>', doc.data());
        });
    })
    .catch((err) => {
        console.log('Error getting documents', err);
    });