Why advanced patterns matter in Express - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a basic Express server that listens on port 3000.

Express

const express = require('express');
const app = express();
app.get('/', (req, res) => {
  res.send('Hello World!');
});
app.listen([1], () => {
  console.log('Server running');
});

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

A80

B8080

C5000

D3000

Attempts:

3 left

💡 Hint

Common Mistakes

Using a port number that is already in use by another service.

Leaving the port number blank or undefined.

The standard port for local Express servers is often 3000. This code starts the server on port 3000.

2fill in blank

medium

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

Express

const express = require('express');
const app = express();
app.use([1]());
app.post('/data', (req, res) => {
  res.json(req.body);
});

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

Aexpress.json

BbodyParser.json

CjsonParser

Dexpress.body

Attempts:

3 left

💡 Hint

Common Mistakes

Using bodyParser.json without importing body-parser.

Using incorrect middleware names.

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

3fill in blank

hard

Fix the error in the route handler to correctly send a JSON response.

Express

app.get('/user', (req, res) => {
  res.[1]({ name: 'Alice' });
});

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

Ajson

Brender

CsendFile

DsendText

Attempts:

3 left

💡 Hint

Common Mistakes

Using res.sendFile for JSON data.

Using res.render without a template engine.

To send a JSON response, use res.json() in Express.

4fill in blank

hard

Fill both blanks to create a route that handles URL parameters and sends them back.

Express

app.get('/user/:[1]', (req, res) => {
  const [2] = req.params.id;
  res.send(`User ID is ${id}`);
});

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

Aid

BuserId

Dparam

Attempts:

3 left

💡 Hint

Common Mistakes

Mismatching parameter names and variable names.

Using undefined variables in the response.

The URL parameter is named 'id', so req.params.id accesses it. The variable to hold it should be 'id' to match the template string.

5fill in blank

hard

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

Express

function logger(req, res, [1]) {
  console.log(`${req.method} ${req.[2]`);
  [3]();
}
app.use(logger);

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

Anext

Burl

DrequestUrl

Attempts:

3 left

💡 Hint

Common Mistakes

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

Using incorrect parameter names.

The third parameter in middleware is 'next' to pass control. The URL is accessed via req.url. Calling next() continues to the next middleware.