Cloud Functions

See the Cloud Functions docs for Firebase.

Functions samples

See the official GitHub repo of Cloud Functions for Firebase sample functions

Mount an Express app

const functions = require('firebase-functions');
const express = require('express');
const cors = require('cors');
const app = express();
// Automatically allow cross-origin requests
app.use(cors({ origin: true }));
// Add middleware to authenticate requests
app.use(myMiddleware);
// build multiple CRUD interfaces:
app.get('/:id', (req, res) => res.send(Widgets.getById(req.params.id)));
app.post('/', (req, res) => res.send(Widgets.create()));
app.put('/:id', (req, res) => res.send(Widgets.update(req.params.id, req.body)));
app.delete('/:id', (req, res) => res.send(Widgets.delete(req.params.id)));
app.get('/', (req, res) => res.send(Widgets.list()));
// Expose Express API as a single Cloud Function:
exports.widgets = functions.https.onRequest(app);

Mount an Express handler

exports.helloWorld = functions.https.onRequest((req, res) => {
res.status(200);
res.send('hello world');
});

Firestore triggers

  • onCreate

  • onUpdate

  • onDelete

  • onWrite

exports.createUser = functions.firestore.document('users/{userId}').onCreate(event => {
// Get an object representing the document
// e.g. {'name': 'Marie', 'age': 66}
var newValue = event.data.data();
// access a particular field as you would any JS property
var name = newValue.name;
// perform desired operations ...
});

Realtime Database triggers

  • onCreate

  • onUpdate

  • onDelete

  • onWrite

exports.makeUppercase = functions.database.ref('/messages/{pushId}/original').onWrite(event => {
// Grab the current value of what was written to the Realtime Database.
const original = event.data.val();
console.log('Uppercasing', event.params.pushId, original);
const uppercase = original.toUpperCase();
// You must return a Promise when performing asynchronous tasks inside a Functions such as
// writing to the Firebase Realtime Database.
// Setting an "uppercase" sibling in the Realtime Database returns a Promise.
return event.data.ref.parent.child('uppercase').set(uppercase);
});

Firebase Authentication

  • onCreate

  • onDelete

exports.sendWelcomeEmail = functions.auth.user().onCreate(event => {
const user = event.data; // The Firebase user.
const email = user.email; // The email of the user.
const displayName = user.displayName; // The display name of the user.
});

Firebase Storage

  • onChange

exports.generateThumbnail = functions.storage.object().onChange(event => {
const object = event.data; // The Storage object.
const fileBucket = object.bucket; // The Storage bucket that contains the file.
const filePath = object.name; // File path in the bucket.
const contentType = object.contentType; // File content type.
const resourceState = object.resourceState; // The resourceState is 'exists' or 'not_exists' (for file/folder deletions).
const metageneration = object.metageneration; // Number of times metadata has been generated. New objects have a value of 1.
// Exit if this is triggered on a file that is not an image.
if (!contentType.startsWith('image/')) {
console.log('This is not an image.');
return;
}
// Get the file name.
const fileName = path.basename(filePath);
// Exit if the image is already a thumbnail.
if (fileName.startsWith('thumb_')) {
console.log('Already a Thumbnail.');
return;
}
// Exit if this is a move or deletion event.
if (resourceState === 'not_exists') {
console.log('This is a deletion event.');
return;
}
// Exit if file exists but is not new and is only being triggered
// because of a metadata change.
if (resourceState === 'exists' && metageneration > 1) {
console.log('This is a metadata change event.');
return;
}
});

Use ImageMagick

const functions = require('firebase-functions');
const gcs = require('@google-cloud/storage')();
const spawn = require('child-process-promise').spawn;
const path = require('path');
const os = require('os');
const fs = require('fs');
exports.generateThumbnail = functions.storage.object().onChange(event => {
const object = event.data;
const fileBucket = object.bucket;
const filePath = object.name;
const contentType = object.contentType;
// Download file from bucket.
const bucket = gcs.bucket(fileBucket);
const tempFilePath = path.join(os.tmpdir(), fileName);
const metadata = { contentType: contentType };
return bucket
.file(filePath)
.download({
destination: tempFilePath,
})
.then(() => {
console.log('Image downloaded locally to', tempFilePath);
// Generate a thumbnail using ImageMagick.
return spawn('convert', [tempFilePath, '-thumbnail', '200x200>', tempFilePath]);
})
.then(() => {
console.log('Thumbnail created at', tempFilePath);
// We add a 'thumb_' prefix to thumbnails file name. That's where we'll upload the thumbnail.
const thumbFileName = `thumb_${fileName}`;
const thumbFilePath = path.join(path.dirname(filePath), thumbFileName);
// Uploading the thumbnail.
return bucket.upload(tempFilePath, { destination: thumbFilePath, metadata: metadata });
// Once the thumbnail has been uploaded delete the local file to free up disk space.
})
.then(() => fs.unlinkSync(tempFilePath));
});