Structured logging with JSON in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the logging library.

Express

const logger = require('[1]');

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

Aexpress

Bpino

Chttp

Dfs

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'express' instead of a logging library.

Using 'fs' which is for file system operations.

We use 'pino' for structured JSON logging in Express apps.

2fill in blank

medium

Complete the code to create a logger instance.

Express

const log = logger({ level: '[1]' });

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

Aerror

Bwarn

Cinfo

Ddebug

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'error' which logs only errors.

Using 'debug' which is very verbose.

Setting level to 'info' logs informational messages and above.

3fill in blank

hard

Fix the error in the logging statement to log a JSON object with message and userId.

Express

log.info({ message: 'User logged in', [1]: 12345 });

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

Auserid

Buser_id

CUserId

DuserId

Attempts:

3 left

💡 Hint

Common Mistakes

Using lowercase or snake_case keys which are inconsistent.

Capitalizing the first letter which is not standard.

The correct camelCase key is 'userId' for consistency.

4fill in blank

hard

Fill both blanks to log an error with message and error code.

Express

log.[1]({ message: 'Failed to save', code: [2] });

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

Aerror

Bwarn

C500

D404

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'warn' instead of 'error' for error logs.

Using 404 which means not found, not server error.

Use 'error' method to log errors and code 500 for server error.

5fill in blank

hard

Fill all three blanks to create a middleware that logs request method, URL, and status code.

Express

app.use((req, res, next) => {
  res.on('finish', () => {
    log.info({ method: req.[1], url: req.[2], status: res.[3] });
  });
  next();
});

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

Amethod

Burl

CstatusCode

Dpath

Attempts:

3 left

💡 Hint

Common Mistakes

Using req.url which includes query string, not just path.

Using res.status instead of res.statusCode.

req.method is HTTP method, req.path is URL path, res.statusCode is response status.