How do Firebase Cloud Functions work and how do you write HTTPS callable functions?

Explanation & Concept

Cloud Functions for Firebase allows running serverless backend code in response to HTTPS requests or Firebase events (such as Firestore document updates, Auth user creation, or Storage uploads).

**Callable Functions** automatically deserialize parameters and inject authentication context (`context.auth`), ensuring secure client-to-server communication.

Code Example

typescript

import { onCall, HttpsError } from "firebase-functions/v2/https";
import { getFirestore } from "firebase-admin/firestore";

export const addAdminRole = onCall(async (request) => {
  // Enforce caller authentication and authorization
  if (!request.auth || !request.auth.token.admin) {
    throw new HttpsError("permission-denied", "Only administrators can assign roles.");
  }
  
  const { targetUid } = request.data;
  const db = getFirestore();
  await db.collection("users").doc(targetUid).update({ role: "admin" });
  
  return { success: true, message: `User ${targetUid} promoted to admin.` };
});

How It Works & Key Takeaways

Callable functions handle CORS, authentication verification, and error serialization automatically.

Mock Test · 1 Questions · Optional

Ready for Realtime Database vs Firestore?

Take a quick test to evaluate yourself, or move straight to the next module.

Beginner1 questions

Skip

Cloud FunctionsBeginner

1Question 1 of 1

typescript

How do Firebase Cloud Functions work and how do you write HTTPS callable functions?

Explanation & Concept

Cloud Functions for Firebase allows running serverless backend code in response to HTTPS requests or Firebase events (such as Firestore document updates, Auth user creation, or Storage uploads).

**Callable Functions** automatically deserialize parameters and inject authentication context (`context.auth`), ensuring secure client-to-server communication.

Code Example

typescript

import { onCall, HttpsError } from "firebase-functions/v2/https";
import { getFirestore } from "firebase-admin/firestore";

export const addAdminRole = onCall(async (request) => {
  // Enforce caller authentication and authorization
  if (!request.auth || !request.auth.token.admin) {
    throw new HttpsError("permission-denied", "Only administrators can assign roles.");
  }
  
  const { targetUid } = request.data;
  const db = getFirestore();
  await db.collection("users").doc(targetUid).update({ role: "admin" });
  
  return { success: true, message: `User ${targetUid} promoted to admin.` };
});

How It Works & Key Takeaways

Callable functions handle CORS, authentication verification, and error serialization automatically.

Mock Test · 1 Questions · Optional

Ready for Realtime Database vs Firestore?

Take a quick test to evaluate yourself, or move straight to the next module.

Beginner1 questions

Skip