Cloud Functions are about serverless event-driven code. Serverless applications have become increasingly popular in recent years. Serverless computing offers several advantages over traditional server-centric infrastructure: avoids the need for server provisioning, offers easier setup, greater scalability, more flexibility, and quicker time to release. With serverless architectures, developers can focus on writing and testing the application.

To build our RESTful API using serverless technology, we use RTDB (i.e. Firebase realtime database) and Firebase cloud functions, which can be wired to respond directly to HTTP requests.

• Prerequisites
• Initialize project
• Local testing
• Deploy

First, create a Firebase project in Firebase console.

We are going to be using node as well as express to host the server-side code and program in server-side Typescript. We also need to write functions locally with the help of firebase CLI. To set up the environment in Linux, follow these steps:

In Linux terminal, install nvm:

$ curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.35.3/install.sh | 

Restart Terminal once before starting using NVM.

Check in the terminal:

$ command -v nvm

Sample output: nvm

Install Node.js and npm:

$ nvm install v12.18.1

Check in the terminal:

$ node --version

Sample output: v12.18.1

$ npm --version

Sample output: 6.14.5

Install Firebase CLI

$ npm install -g firebase-tools

Can check its version

$ firebase --version

In Linux terminal, run:

$ mkdir folderName
$ cd folderName/
$ firebase login 

-> “Y” -> log in and allow access

$ firebase init

Select “Database, Functions, Hosting, Emulators” Select “Use an existing project” -> input projectID

Select Typescript

Type “Y” except “Configure as a single-page app (rewrite all urls to /index.html)?”

Select "Functions, Database, Hosting" for emulators

Should see ✔ Firebase initialization complete!

Then, run:

$ cd folderName/functions
$ npm install --save express body-parser

There are three important things under the functions directory.

• index.js is a Javascript file where we define all the functions.
• Package.json is a Json file used by node, containing modules and their dependencies (e.g. Firebase Admin, Firebase functions) for the usage of the functions.
• node_modules is a folder where NPM installed those modules during the setup.

Run:

$ npm run lint
$ npm run build
$ firebase emulators:start

Check the output for the URL:

http://localhost:5001/projectID/us-central1/ROUTE

Three different ways to check the output:

a. Use curl in the terminal

b. Enter the url in a browser

c. Use Postman

Run:

$ firebase deploy

Check the output for the URL:

$ curl https://step95-2020.firebaseapp.com/ROUTE -H "Authorization: bearer $(gcloud auth print-identity-token)"