Request size limits in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set a JSON body size limit of 1mb in Express.

Express

app.use(express.json({ limit: '[1]' }));

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

A1mbs

B1mb

C1000kb

Done_mb

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect units like '1mbs' or 'one_mb'.

Passing a number without quotes.

The limit option accepts a string like '1mb' to set the max request body size.

2fill in blank

medium

Complete the code to set a URL-encoded body size limit of 500kb in Express.

Express

app.use(express.urlencoded({ extended: true, limit: '[1]' }));

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

A500kb

B500mb

C0.5mb

D500

Attempts:

3 left

💡 Hint

Common Mistakes

Using '500' without units causes no size limit.

Using '500mb' is too large for this example.

The limit option for express.urlencoded sets the max size. '500kb' means 500 kilobytes.

3fill in blank

hard

Fix the error in this code that tries to limit JSON body size to 2mb.

Express

app.use(express.json({ limit: [1] }));

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

A'2mb'

B2

C"2mb"

D2mb

Attempts:

3 left

💡 Hint

Common Mistakes

Passing 2mb without quotes causes a syntax error.

Passing a number like 2 means 2 bytes, which is too small.

The limit value must be a string with quotes, like '2mb'. Without quotes, it causes an error.

4fill in blank

hard

Fill both blanks to limit JSON and URL-encoded bodies to 1mb in Express.

Express

app.use(express.json({ limit: '[1]' }));
app.use(express.urlencoded({ extended: true, limit: '[2]' }));

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

A1mb

B1000kb

C1kb

D10mb

Attempts:

3 left

💡 Hint

Common Mistakes

Using '1kb' is too small for typical requests.

Using '10mb' is larger than requested.

Both express.json and express.urlencoded accept size limits as strings. '1mb' and '1000kb' are equivalent.

5fill in blank

hard

Fill all three blanks to create an Express app limiting JSON to 2mb, URL-encoded to 1mb, and text bodies to 500kb.

Express

app.use(express.json({ limit: '[1]' }));
app.use(express.urlencoded({ extended: true, limit: '[2]' }));
app.use(express.text({ limit: '[3]' }));

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

A2mb

B1mb

C500kb

D5mb

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the size limits for each parser.

Using numbers without quotes.

Each middleware sets a size limit string: JSON to '2mb', URL-encoded to '1mb', and text to '500kb'.

Practice

1. What is the main purpose of setting a request size limit in Express middleware like express.json()?

easy

A. To increase the speed of the server by caching requests

B. To prevent very large requests from slowing down or crashing the server

C. To automatically compress large requests for faster processing

D. To allow unlimited request sizes for flexibility

Solution

1. Step 1: Understand the role of request size limits

   Request size limits help protect the server from very large requests that can slow it down or cause crashes.

2. Step 2: Identify the correct purpose in Express middleware

   The limit option in express.json() sets this size limit to keep the server safe and responsive.

3. Final Answer:

   To prevent very large requests from slowing down or crashing the server -> Option B

4. Quick Check:

   Request size limit = prevent server overload [OK]

Hint: Request size limits protect server from overload [OK]

Common Mistakes:

• Thinking it speeds up requests by caching
• Confusing size limit with compression
• Assuming unlimited size is better

2. Which of the following is the correct way to set a 10kb limit on JSON request bodies in Express?

easy

A. app.use(express.json({ sizeLimit: 10 }))

B. app.use(express.json(limit = 10))

C. app.use(express.json({ maxSize: '10kb' }))

D. app.use(express.json({ limit: '10kb' }))

Solution

1. Step 1: Recall the correct option name for size limit

   The correct option to set request size limit in express.json() is limit.

2. Step 2: Check the correct syntax for setting 10kb

   The value should be a string with units, like '10kb'. So { limit: '10kb' } is correct.

3. Final Answer:

   app.use(express.json({ limit: '10kb' })) -> Option D

4. Quick Check:

   Use limit: '10kb' option [OK]

Hint: Use limit option with string size like '10kb' [OK]

Common Mistakes:

• Using wrong option names like sizeLimit or maxSize
• Passing number without units
• Using assignment inside options object

3. Given this Express setup:

app.use(express.json({ limit: '5kb' }));
app.post('/data', (req, res) => {
  res.send('Received');
});

What happens if a client sends a JSON body of 10kb to /data?

medium

A. The server rejects the request with a 413 Payload Too Large error

B. The server ignores the body and responds with an empty object

C. The server crashes due to memory overflow

D. The server accepts the request and responds with 'Received'

Solution

1. Step 1: Understand the limit setting effect

   The limit is set to 5kb, so any request body larger than 5kb will be rejected.

2. Step 2: Identify Express behavior on large requests

   Express responds with a 413 Payload Too Large error when the body exceeds the limit.

3. Final Answer:

   The server rejects the request with a 413 Payload Too Large error -> Option A

4. Quick Check:

   Request > limit = 413 error [OK]

Hint: Requests over limit get 413 error response [OK]

Common Mistakes:

• Assuming server accepts large requests anyway
• Thinking server crashes instead of error response
• Believing server ignores body silently

4. Consider this Express code snippet:

app.use(express.json({ limit: 10000 }));

What is the problem with this code regarding request size limits?

medium

A. There is no problem; this code sets a 10kb limit correctly

B. The limit option is not supported by express.json()

C. The limit value is too small and will reject all requests

D. The limit value should be a string with units like '10kb', not a number

Solution

1. Step 1: Check the type of the limit option value

   The limit option accepts both numbers (in bytes) and strings with units like '10kb'.

2. Step 2: Understand the effect of passing a number

   Passing 10000 sets the limit to 10000 bytes (approximately 10kb), which works correctly.

3. Final Answer:

   There is no problem; this code sets a 10kb limit correctly -> Option A

4. Quick Check:

   limit: number = bytes [OK]

Hint: Limit accepts number (bytes) or string with units [OK]

Common Mistakes:

• Thinking it must be string with units only
• Thinking limit option is unsupported
• Assuming number means bytes automatically is wrong

5. You want to accept JSON requests up to 1mb but URL-encoded form data only up to 100kb in your Express app. Which setup correctly applies these limits?

hard

A. app.use(express.json({ limit: 100 * 1024 }));\napp.use(express.urlencoded({ limit: 1 * 1024 * 1024, extended: false }));

B. app.use(express.json({ maxSize: '1mb' }));\napp.use(express.urlencoded({ maxSize: '100kb', extended: true }));

C. app.use(express.json({ limit: '1mb' }));\napp.use(express.urlencoded({ limit: '100kb', extended: true }));

D. app.use(express.json({ limit: '100kb' }));\napp.use(express.urlencoded({ limit: '1mb', extended: true }));

Solution

1. Step 1: Set JSON request limit to 1mb correctly

   Use express.json({ limit: '1mb' }) to set JSON body limit to 1 megabyte.

2. Step 2: Set URL-encoded form data limit to 100kb correctly

   Use express.urlencoded({ limit: '100kb', extended: true }) to set form data limit to 100 kilobytes.

3. Step 3: Verify option names and values

   Both use the correct limit option with string sizes and proper extended flag for URL-encoded.

4. Final Answer:

   app.use(express.json({ limit: '1mb' })); app.use(express.urlencoded({ limit: '100kb', extended: true })); -> Option C

5. Quick Check:

   Use limit strings per middleware type [OK]

Hint: Set limits separately with correct units and options [OK]

Common Mistakes:

• Swapping limits between JSON and URL-encoded
• Using numbers instead of strings for limits
• Using wrong option names like maxSize