Firebase Cheatsheet

Quick reference for Firebase Realtime Database and Authentication Web APIs.

Initialization

import { initializeApp } from 'firebase/app'
import { getDatabase, ref, set, get, child, onValue } from 'firebase/database'

const firebaseConfig = {
  apiKey: "API_KEY",
  authDomain: "project-id.firebaseapp.com",
  databaseURL: "https://project-id.firebaseio.com",
  projectId: "project-id"
}

const app = initializeApp(firebaseConfig)
const db = getDatabase(app)

Data Manipulation

Writing Data (set)

set(ref(db, 'users/' + userId), {
  username: "AlanTuring",
  email: "[email protected]"
})

Reading Data Once (get)

const dbRef = ref(db)
get(child(dbRef, `users/${userId}`)).then((snapshot) => {
  if (snapshot.exists()) {
    console.log(snapshot.val())
  } else {
    console.log("No data available")
  }
}).catch((error) => {
  console.error(error)
})

Realtime Subscriptions (onValue)

const starCountRef = ref(db, 'posts/' + postId + '/starCount')
onValue(starCountRef, (snapshot) => {
  const data = snapshot.val()
  console.log('Updated star count:', data)
})

Pushing Lists of Data

import { push } from 'firebase/database'

const postListRef = ref(db, 'posts')
const newPostRef = push(postListRef)
set(newPostRef, {
  title: "New Post Title",
  author: "grace"
})

Queries and Sorting

import { query, orderByChild, limitToFirst } from 'firebase/database'

const recentPostsQuery = query(
  ref(db, 'posts'),
  orderByChild('createdAt'),
  limitToFirst(20)
)
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