This is a bit simpler a question than I tend to like to come here with but I\'ve been driving myself up the wall trying to find an answer to this and I absolutely cannot-
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First Create a Handler function,
function bookIdHandler(req,res){
let bookId= req.params.bookId;
//your code goes here
}
You can just pass an Express App object to cloud function routes
const express = require('express');
const app = express();
app.get('users/:userId/:bookId', bookIdHandler);
//++ any other express endpoints
// Expose Express API as a single Cloud Function:
exports.widgets = functions.https.onRequest(app);
Ref:How its mentioned in firebase docs