Notes

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
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const functions = require('firebase-functions');
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const express = require('express');
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const cors = require('cors');
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const app = express();
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​
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// Automatically allow cross-origin requests
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app.use(cors({ origin: true }));
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​
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// Add middleware to authenticate requests
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app.use(myMiddleware);
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​
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// build multiple CRUD interfaces:
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app.get('/:id', (req, res) => res.send(Widgets.getById(req.params.id)));
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app.post('/', (req, res) => res.send(Widgets.create()));
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app.put('/:id', (req, res) => res.send(Widgets.update(req.params.id, req.body)));
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app.delete('/:id', (req, res) => res.send(Widgets.delete(req.params.id)));
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app.get('/', (req, res) => res.send(Widgets.list()));
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​
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// Expose Express API as a single Cloud Function:
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exports.widgets = functions.https.onRequest(app);
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Mount an Express handler
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exports.helloWorld = functions.https.onRequest((req, res) => {
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  res.status(200);
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  res.send('hello world');
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});
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Firestore triggers
onCreate
onUpdate
onDelete
onWrite
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exports.createUser = functions.firestore.document('users/{userId}').onCreate(event => {
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  // Get an object representing the document
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  // e.g. {'name': 'Marie', 'age': 66}
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  var newValue = event.data.data();
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​
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  // access a particular field as you would any JS property
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  var name = newValue.name;
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​
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  // perform desired operations ...
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});
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Realtime Database triggers
onCreate
onUpdate
onDelete
onWrite
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exports.makeUppercase = functions.database.ref('/messages/{pushId}/original').onWrite(event => {
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  // Grab the current value of what was written to the Realtime Database.
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  const original = event.data.val();
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  console.log('Uppercasing', event.params.pushId, original);
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  const uppercase = original.toUpperCase();
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  // You must return a Promise when performing asynchronous tasks inside a Functions such as
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  // writing to the Firebase Realtime Database.
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  // Setting an "uppercase" sibling in the Realtime Database returns a Promise.
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  return event.data.ref.parent.child('uppercase').set(uppercase);
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});
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Firebase Authentication
onCreate
onDelete
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exports.sendWelcomeEmail = functions.auth.user().onCreate(event => {
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  const user = event.data; // The Firebase user.
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​
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  const email = user.email; // The email of the user.
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  const displayName = user.displayName; // The display name of the user.
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});
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Firebase Storage
onChange
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exports.generateThumbnail = functions.storage.object().onChange(event => {
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  const object = event.data; // The Storage object.
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​
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  const fileBucket = object.bucket; // The Storage bucket that contains the file.
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  const filePath = object.name; // File path in the bucket.
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  const contentType = object.contentType; // File content type.
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  const resourceState = object.resourceState; // The resourceState is 'exists' or 'not_exists' (for file/folder deletions).
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  const metageneration = object.metageneration; // Number of times metadata has been generated. New objects have a value of 1.
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​
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  // Exit if this is triggered on a file that is not an image.
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  if (!contentType.startsWith('image/')) {
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    console.log('This is not an image.');
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    return;
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  }
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​
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  // Get the file name.
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  const fileName = path.basename(filePath);
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  // Exit if the image is already a thumbnail.
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  if (fileName.startsWith('thumb_')) {
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    console.log('Already a Thumbnail.');
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    return;
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  }
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​
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  // Exit if this is a move or deletion event.
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  if (resourceState === 'not_exists') {
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    console.log('This is a deletion event.');
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    return;
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  }
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​
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  // Exit if file exists but is not new and is only being triggered
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  // because of a metadata change.
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  if (resourceState === 'exists' && metageneration > 1) {
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    console.log('This is a metadata change event.');
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    return;
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  }
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});
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Use ImageMagick
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const functions = require('firebase-functions');
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const gcs = require('@google-cloud/storage')();
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const spawn = require('child-process-promise').spawn;
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const path = require('path');
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const os = require('os');
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const fs = require('fs');
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​
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exports.generateThumbnail = functions.storage.object().onChange(event => {
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  const object = event.data;
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​
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  const fileBucket = object.bucket;
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  const filePath = object.name;
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  const contentType = object.contentType;
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​
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  // Download file from bucket.
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  const bucket = gcs.bucket(fileBucket);
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  const tempFilePath = path.join(os.tmpdir(), fileName);
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  const metadata = { contentType: contentType };
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  return bucket
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    .file(filePath)
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    .download({
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      destination: tempFilePath,
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    })
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    .then(() => {
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      console.log('Image downloaded locally to', tempFilePath);
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      // Generate a thumbnail using ImageMagick.
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      return spawn('convert', [tempFilePath, '-thumbnail', '200x200>', tempFilePath]);
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    })
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    .then(() => {
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      console.log('Thumbnail created at', tempFilePath);
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      // We add a 'thumb_' prefix to thumbnails file name. That's where we'll upload the thumbnail.
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      const thumbFileName = `thumb_${fileName}`;
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      const thumbFilePath = path.join(path.dirname(filePath), thumbFileName);
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      // Uploading the thumbnail.
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      return bucket.upload(tempFilePath, { destination: thumbFilePath, metadata: metadata });
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      // Once the thumbnail has been uploaded delete the local file to free up disk space.
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    })
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    .then(() => fs.unlinkSync(tempFilePath));
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});
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Cloud Functions for Firebase - Previous

Challenge

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Introduction

Last modified 3yr ago

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Contents

Cloud Functions

Mount an Express app

Mount an Express handler

Firestore triggers

Realtime Database triggers

Firebase Authentication

Firebase Storage

Use ImageMagick