<p>Firebase Firestore is the NoSQL database infrastructure by Google. I really like the almost effortless way of setting up a database-to-client connection on pretty much any platform provided by Firestore.</p><p>So, as a fan of Firestore, I will list the common and maybe even some uncommon but very useful queries you might need to use for Firestore as concisely as possible.</p><p>NOTE: This is not an introductory blog on Firestore or Firebase. This is for the advanced user who has prior experience with Firestore.</p><blockquote><p>Table of content:</p><ol><li><p>Read a single document.</p></li><li><p>Write a single document.</p></li><li><p>Query a collection to fetch a limited number of documents.</p></li><li><p>Push a new document to a collection with a random ID.</p></li></ol></blockquote><p></p><h3>1. Read a single document:</h3><pre><code>import { doc, getDoc, getFirestore } from "firebase/firestore";

// Create a reference to the document you need to fetch
const docRef = doc(getFirestore(), "collectionId", "documentId");

// Run the promise using getDoc to return the document
const docSnap = await getDoc(docRef);</code></pre><p></p><h3>2. Write a single document:</h3><pre><code>import { doc, setDoc } from "firebase/firestore"; 

// Create a reference to the document you want to write to
const docRef = doc(getFirestore(), "collectionId", "documentId");

// newData has to be an object with key-value maps
const newData = {
  displayName: "New Data",
  email: "newdata@newdata.com"
};

// Run the promise using setDoc to write the new Data
await setDoc(docRef, newData);</code></pre><p></p><h3>3. Query a collection to fetch a limited number of documents:</h3><pre><code>import {
  getFirestore,
  collection,
  query,
  where,
  startAfter,
  limit,
  getDocs,
  orderBy,
  doc,
  getDoc,
} from "firebase/firestore"; 


// Create a reference to the collection you want fetch document(s) from
const collectionRef = collection(getFirestore(), "collectionId");

// Write the query
 const q = query(collectionRef,

    // Set a where condition
    where("state", "==", "PUBLIC"),

    // Set a ordering condition.
    orderBy("postCreated", "desc"),

    // Set a cursor point that dictates where to start querying from
    startAfter(13209328),

    // Limit to how many documents should be fetched from the collection
    limit(7),
);

// Run the query to fetch the documents from the collection
const docsSnapshot = await getDocs(q);</code></pre><p></p><h3>4. Push a new document to a collection with a random ID:</h3><pre><code>import { collection, addDoc } from "firebase/firestore"; 

// Create a reference to the collection you push a document to
const collectionRef = collection(getFirestore(), "collectionId");

// newData has to be an object with key-value maps
const newData = {
  displayName: "New Data",
  email: "newdata@newdata.com"
};

// Run the promise using addDoc to push this data as a new document with a random id
const docRef = await addDoc(collectionRef, newData);</code></pre>

Firebase Firestore is the NoSQL database infrastructure by Google. I really like the almost effortless way of setting up a databas...

Aneek Rahman

Firestore: Common Firebase Firestore queries Cheatsheet