firebase-cloud-function.ts

import * as functions from "firebase-functions";
import { Request, Response } from "firebase-functions";
import * as cors from 'cors';
const corsHandler = cors({origin: true});

// Start writing Firebase Functions
// https://firebase.google.com/docs/functions/typescript

export const helloWorld = functions.https.onRequest((request: Request, response: Response) => {
  corsHandler(request, response, () => {
    functions.logger.info("Hello logs!", {structuredData: true});
    // browsers like chrome need these headers to be present in response if the api is called from other than its base domain
    response.set("Access-Control-Allow-Origin", "*"); // you can also whitelist a specific domain like "http://127.0.0.1:4000"
    response.set("Access-Control-Allow-Headers", "Content-Type");
  
    response.json({"message": "Hello from Firebase!"});
  });
});