Explore Firebase's unified development platform; gain insights into authentication, Firestore, Cloud Functions, and deployment with CLI. Delve into hands-on web application creation and comprehensive tools.

firebase-lessons.tar.gz

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Firebase lesson

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Firebase is a unified application development platform to create, deploy, and monitor web and mobile experiences. It unites common product functions in a single platform, freeing engineers to create functionality and user experience rather than having to create the infrastructure.

This course is a comprehensive introduction to the Firebase 9 SDK through hands-on development of a web application. You’ll start with basic concepts and functions like authentication, database, and Cloud Storage with Firestore. You’ll then learn Cloud Functions for Firebase, environment variables, Security Rules, and hosting capabilities before deploying an application using the command line interface (CLI). At each step, you’ll get hands-on exercises to modify the code, see real-time output in your browser, and finish with an assessment.

By the end of this course, you’ll have all the tools you need to build and deploy a web application with the Firebase 9 SDK—the latest version of Firebase.

A Complete Guide to Firebase on the Web

There are multiple ways to read data from the Cloud Firestore database. The method used depends on the behavior desired for our application. Let’s dive into these methods!

# Use the `getDoc` function
The `getDoc` function retrieves the contents of a single document in the database. As its argument, this function takes a reference to the document to be fetched. It returns a JavaScript promise that resolves with a snapshot of the document’s current content.

Within the document’s snapshot, we have access to some Javascript _methods_ we can use to check each document’s existence and obtain the data inside it:



import { doc, getFirestore, getDoc } from "firebase/firestore";
import { firebaseApp } from "../services/firebase";

const firestore = getFirestore(firebaseApp);

const docRef = doc(firestore, "users/test@educative.io");

export const retrieveDoc = async () => {
  const docSnapshot = await getDoc(docRef);

  if (docSnapshot.exists()) {
    const docData = docSnapshot.data();
    console.log(docData);
  }
};

In _line 11_, we use the `exists` method to check if there is a document at the location referenced by the `docRef` instance. If there is no document at the location, the `exists` method returns `false`. Assuming a document does exist at the location, the `data` method to obtains the data in the document, as shown in **line 12**.

# Use the `getDocs` function
For cases when we need to get all the documents within a collection, we must use the `getDocs` function. The `getDocs` function is imported from the `firebase/firestore` subpackage. As an argument, it takes a reference to the collection location and returns a JavaScript promise that resolves with a snapshot of the collection.

We can iterate over the snapshot received by calling the `forEach` method on it. This takes a callback function to be executed on each document in the snapshot. Here, we can use the `data` method to obtain the document’s content:


Learn how to get data from the Cloud Firestore database and discover how to retrieve real-time data from Cloud Firestore.

Introduction

Get Started with Firebase

Firebase Authentication

The Firebase Realtime Database

Cloud Firestore

Cloud Storage for Firebase

The Firebase CLI

Cloud Functions

Environment Variables in Firebase

Firebase Security Rules

Firebase Hosting

Firebase Assessment

Conclusion

Appendix

Read data from Cloud Firestore

Use the `getDoc` function