Why production setup matters in Express - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start an Express server listening on port 3000.

Express

const express = require('express');
const app = express();
app.listen([1], () => {
  console.log('Server running');
});

Drag options to blanks, or click blank then click option'

A3000

Bapp

C'3000'

Dexpress

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of a number for the port.

Passing the app or express object instead of a port number.

The listen method needs a number for the port. Using 3000 starts the server on port 3000.

2fill in blank

medium

Complete the code to add a middleware that parses JSON bodies in requests.

Express

const express = require('express');
const app = express();
app.use([1]());

Drag options to blanks, or click blank then click option'

AbodyParser.json

Bexpress.json

CjsonParser

Dexpress.body

Attempts:

3 left

💡 Hint

Common Mistakes

Using bodyParser.json without importing body-parser.

Using incorrect method names like express.body.

Express has a built-in middleware called express.json() to parse JSON request bodies.

3fill in blank

hard

Fix the error in the code to properly handle errors in Express.

Express

app.use((err, req, res, [1]) => {
  console.error(err.stack);
  res.status(500).send('Something broke!');
});

Drag options to blanks, or click blank then click option'

Anext

Berror

Cresponse

Drequest

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong parameter names like 'error' or 'response' instead of 'next'.

Missing the fourth parameter entirely.

The error-handling middleware in Express must have four arguments: err, req, res, next. The last one is next.

4fill in blank

hard

Fill both blanks to create a route that responds with JSON and sets a custom header.

Express

app.get('/info', (req, res) => {
  res.set('[1]', '[2]').json({ message: 'Hello' });
});

Drag options to blanks, or click blank then click option'

AX-Custom-Header

BContent-Type

CCustomValue

Dapplication/json

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Content-Type' header incorrectly here.

Not chaining the methods properly.

To add a custom header, use res.set('X-Custom-Header', 'CustomValue'). The JSON response is sent after setting the header.

5fill in blank

hard

Fill all three blanks to create a middleware that logs request method, URL, and then calls next.

Express

app.use(([1], [2], [3]) => {
  console.log(`$[1].method} $[2].url}`);
  [3]();
});

Drag options to blanks, or click blank then click option'

Areq

Bres

Cnext

Drequest

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'request' instead of 'req'.

Forgetting to call next() causing the request to hang.

Middleware functions receive req, res, and next. We log req.method and req.url, then call next() to continue.