Challenge - 5 Problems

🎖️

Catch-All Mastery

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Test your skills under time pressure!

❓ component_behavior

intermediate

2:00remaining

What is the output when using app.all for a catch-all route?

Consider this Express code snippet:

const express = require('express');
const app = express();

app.all('*', (req, res) => {
  res.send('Catch-all with app.all');
});

app.listen(3000);

What will a GET request to /anything respond with?

Express

const express = require('express');
const app = express();

app.all('*', (req, res) => {
  res.send('Catch-all with app.all');
});

app.listen(3000);

AThe server throws an error because app.all cannot use '*' as a path.

BThe server responds with 404 Not Found because no GET route is defined.

CThe server responds with 'Catch-all with app.all' only for POST requests.

DThe server responds with 'Catch-all with app.all' for any HTTP method and path.

Attempts:

2 left

❓ component_behavior

intermediate

2:00remaining

How does app.use behave as a catch-all middleware?

Given this Express setup:

const express = require('express');
const app = express();

app.use((req, res) => {
  res.send('Catch-all with app.use');
});

app.listen(3000);

What happens when a GET request is made to /random?

Express

const express = require('express');
const app = express();

app.use((req, res) => {
  res.send('Catch-all with app.use');
});

app.listen(3000);

AThe server responds only if the request method is POST.

BThe server responds with 404 Not Found because no route matches.

CThe server responds with 'Catch-all with app.use' for any path and method.

DThe server throws an error because app.use requires a path argument.

Attempts:

2 left

📝 Syntax

advanced

2:00remaining

Which option causes a syntax error when trying to create a catch-all route?

Which of these Express route definitions will cause a syntax error?

Aapp.all('*', (req, res) => res.send('All methods catch-all'));

Bapp.all((req, res) => res.send('Missing path argument'));

Capp.use((req, res) => res.send('Use without path catch-all'));

Dapp.use('*', (req, res) => res.send('Use with path catch-all'));

Attempts:

2 left

❓ state_output

advanced

2:00remaining

What is the response order when both app.use and app.all catch-all handlers exist?

Consider this Express code:

const express = require('express');
const app = express();

app.use((req, res, next) => {
  res.write('Use start - ');
  next();
});

app.all('*', (req, res) => {
  res.end('All end');
});

app.listen(3000);

What will a GET request to /test respond with?

Express

const express = require('express');
const app = express();

app.use((req, res, next) => {
  res.write('Use start - ');
  next();
});

app.all('*', (req, res) => {
  res.end('All end');
});

app.listen(3000);

AThe response is 'Use start - All end'.

BThe response is 'All end' only.

CThe response is 'Use start - ' only, and the request hangs.

DThe server throws an error because res.write and res.end cannot be mixed.

Attempts:

2 left

🔧 Debug

expert

3:00remaining

Why does this catch-all middleware never respond?

Look at this Express code:

const express = require('express');
const app = express();

app.use((req, res, next) => {
  next();
  res.send('Catch-all response');
});

app.listen(3000);

Why does a request to any path never get the 'Catch-all response'?

Express

const express = require('express');
const app = express();

app.use((req, res, next) => {
  next();
  res.send('Catch-all response');
});

app.listen(3000);

ABecause calling next() passes control and the response is sent after, which is ignored.

BBecause res.send must be called before next(), otherwise it causes a syntax error.

CBecause app.use requires a path argument to respond.

DBecause res.send cannot be used inside middleware.

Attempts:

2 left