Log levels and when to use them in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to log an informational message using Express's logger.

Express

app.use((req, res, next) => { console.[1]('Request received'); next(); });

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

Aerror

Binfo

Cwarn

Ddebug

Attempts:

3 left

💡 Hint

Common Mistakes

Using error or warn for normal request logs.

The info log level is used for general informational messages like requests received.

2fill in blank

medium

Complete the code to log a warning when a deprecated API endpoint is accessed.

Express

app.get('/old-endpoint', (req, res) => { console.[1]('Deprecated endpoint used'); res.send('Deprecated'); });

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

Awarn

Bdebug

Cinfo

Derror

Attempts:

3 left

💡 Hint

Common Mistakes

Using info or error instead of warn for deprecation notices.

The warn level is appropriate for deprecated features to alert developers without stopping the app.

3fill in blank

hard

Fix the error in the code to log an error message when a server error occurs.

Express

app.use((err, req, res, next) => { console.[1]('Server error:', err); res.status(500).send('Error'); });

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

Awarn

Bdebug

Cinfo

Derror

Attempts:

3 left

💡 Hint

Common Mistakes

Using warn or info for actual errors.

The error log level is used to log serious problems like server errors.

4fill in blank

hard

Fill both blanks to log detailed debugging information only when debugging is enabled.

Express

if (process.env.DEBUG) { console.[1]('Debug info:', [2]); }

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

Adebug

Berror

Creq

Dinfo

Attempts:

3 left

💡 Hint

Common Mistakes

Using info or error for debug logs.

Logging wrong variables.

Use debug level for detailed logs and req to show request details.

5fill in blank

hard

Fill all three blanks to create a middleware that logs errors and warns about slow responses.

Express

app.use((req, res, next) => { const start = Date.now(); res.on('finish', () => { const duration = Date.now() - [1]; if (duration > [2]) { console.[3](`Slow response: ${duration}ms`); } }); next(); });

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

Astart

B1000

Cwarn

Dres

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong variable names.

Logging slow responses as errors or info.

The variable start holds the start time, 1000 ms is the threshold, and warn logs slow responses as warnings.