Aquí está mi código de archivo server.js , seguido del mensaje de error completo en el navegador y después de hacer clic en el botón Enviar.

 const express = require('express'); const bodyParser = require('body-parser'); const MongoClient = require('mongodb').MongoClient; const app = express(); MongoClient.connect('mongodb+srv://star:wars123@clusterstar2.j9vfh.mongodb.net/myFirstDatabase?retryWrites=true&w=majority', { useUnifiedTopology: true }) .then(client => { console.log('Connected to Database'); const db = client.db('star-wars-quotes'); // "star-wars-quotes" is the db name const quotesCollection = db.collection('quotes'); }) .catch(error => console.error(error)); app.use(express.urlencoded({ extended: true })); app.use(express.json()); app.get('/', (req, res) => { res.sendFile(__dirname + '/index.html'); }); app.post('/quotes', (req, res) => { quotesCollection.insertOne(req.body) .then(result => { console.log(result); }) .catch(error => console.error(error)); }); app.listen(3000, () => console.log('Listening on port 3000'));

A continuación se muestra el error visto:

 ReferenceError: quotesCollection is not defined at C:\Users\user\Desktop\MERN\crud-express-mongo\server.js:28:5 at Layer.handle [as handle_request] (C:\Users\user\Desktop\MERN\crud-express-mongo\node_modules\express\lib\router\layer.js:95:5) at next (C:\Users\user\Desktop\MERN\crud-express-mongo\node_modules\express\lib\router\route.js:137:13) at Route.dispatch (C:\Users\user\Desktop\MERN\crud-express-mongo\node_modules\express\lib\router\route.js:112:3) at Layer.handle [as handle_request] (C:\Users\user\Desktop\MERN\crud-express-mongo\node_modules\express\lib\router\layer.js:95:5) at C:\Users\user\Desktop\MERN\crud-express-mongo\node_modules\express\lib\router\index.js:281:22 at Function.process_params (C:\Users\user\Desktop\MERN\crud-express-mongo\node_modules\express\lib\router\index.js:335:12) at next (C:\Users\user\Desktop\MERN\crud-express-mongo\node_modules\express\lib\router\index.js:275:10) at jsonParser (C:\Users\user\Desktop\MERN\crud-express-mongo\node_modules\body-parser\lib\types\json.js:101:7) at Layer.handle [as handle_request] (C:\Users\user\Desktop\MERN\crud-express-mongo\node_modules\express\lib\router\layer.js:95:5)