HTTP caching headers (ETag, Cache-Control) in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set a Cache-Control header that tells browsers to cache the response for 1 hour.

Express

app.get('/data', (req, res) => {
  res.set('[1]', 'public, max-age=3600');
  res.send({ message: 'Hello' });
});

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

AExpires

BContent-Type

CETag

DCache-Control

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Content-Type' instead of 'Cache-Control'.

Confusing 'ETag' with cache duration headers.

The Cache-Control header controls how browsers cache responses. Setting it to public, max-age=3600 means the response can be cached for 3600 seconds (1 hour).

2fill in blank

medium

Complete the code to generate an ETag header using the express built-in method.

Express

app.get('/resource', (req, res) => {
  res.[1]();
  res.send('Resource content');
});

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

Aetag

BsetETag

CgenerateETag

DsetHeader

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to use 'setHeader' directly without generating ETag.

Using non-existent methods like 'generateETag'.

Express has a built-in etag() method to generate and set the ETag header automatically.

3fill in blank

hard

Fix the error in the code to properly check the client's ETag and respond with 304 if it matches.

Express

app.get('/file', (req, res) => {
  const etag = '12345';
  if (req.headers['if-none-match'] === [1]) {
    res.status(304).end();
  } else {
    res.set('ETag', etag);
    res.send('File content');
  }
});

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

AETag

Betag

C'etag'

D'ETag'

Attempts:

3 left

💡 Hint

Common Mistakes

Comparing to the string 'etag' instead of the variable etag.

Using 'ETag' which is not defined as a variable.

The variable etag holds the ETag string. We compare the header value to this variable without quotes.

4fill in blank

hard

Fill both blanks to set Cache-Control to no-store and disable ETag generation.

Express

app.use((req, res, next) => {
  res.set('[1]', 'no-store');
  app.disable('[2]');
  next();
});

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

ACache-Control

Betag

CETag

DCache

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'ETag' instead of 'etag' in app.disable.

Setting wrong header names like 'Cache'.

Setting Cache-Control to no-store tells browsers not to cache. Disabling etag stops Express from generating ETags.

5fill in blank

hard

Fill both blanks to create a middleware that sets Cache-Control to private, sets ETag, and sends JSON response.

Express

app.get('/profile', (req, res) => {
  res.set('[1]', 'private, max-age=600');
  res.[2]();
  res.send({ user: 'Alice', id: 1, });
});

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

ACache-Control

Betag

C,

D;

Attempts:

3 left

💡 Hint

Common Mistakes

Using semicolon instead of comma in JSON object.

Forgetting to call etag() method.

Setting wrong header name.

The middleware sets Cache-Control to private with max-age 600 seconds, calls etag() to generate the ETag header, and sends a JSON object with a comma separating properties.