Winston for application logging in Express - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this Winston logger configuration?

Given the following Winston logger setup in an Express app, what will be the output when logger.info('Server started') is called?

Express

const winston = require('winston');

const logger = winston.createLogger({
  level: 'info',
  format: winston.format.simple(),
  transports: [
    new winston.transports.Console()
  ]
});

logger.info('Server started');

A Error: No output

B Server started

C [INFO] Server started

D info: Server started

💡 Hint

Look at the format used in the logger configuration.

The simple format outputs the log level followed by the message, separated by a colon and space.

🧠 Conceptual

intermediate

Which transport writes logs to a file in Winston?

In Winston, which transport class is used to save logs into a file?

A winston.transports.File

B winston.transports.Console

C winston.transports.Http

D winston.transports.Stream

💡 Hint

Think about the transport that deals with files.

The File transport writes logs to a file on disk.

❓ Troubleshoot

advanced

Why does this Winston logger not output any logs?

Consider this Winston logger setup. Why does calling logger.debug('Debug message') produce no output?

Express

const winston = require('winston');

const logger = winston.createLogger({
  level: 'info',
  transports: [new winston.transports.Console()]
});

logger.debug('Debug message');

A Because 'debug' is not a valid log level in Winston

B Because the Console transport is missing a format option

C Because the logger level is set to 'info', which ignores 'debug' level logs

D Because the logger is missing a file transport

💡 Hint

Check the logger's level setting and how it filters messages.

Winston only logs messages at or above the set level. 'debug' is lower than 'info', so it is ignored.

🔀 Workflow

advanced

Order the steps to add a timestamp to Winston logs

Put these steps in the correct order to configure Winston to include timestamps in log messages.

A 2,1,3,4

B 1,2,3,4

C 1,3,2,4

D 1,2,4,3

💡 Hint

Think about how you build the format step by step.

First create the logger, then add timestamp format, then define how to print it, then assign the format.

✅ Best Practice

expert

What is the best practice for handling uncaught exceptions with Winston?

Which option correctly shows how to configure Winston to handle uncaught exceptions and log them to a file?

A Add an exceptions handler with a File transport in the logger configuration.

B Use process.on('uncaughtException') to manually log errors without Winston.

C Set the logger level to 'error' and rely on default behavior.

D Wrap all code in try-catch blocks and log errors with console.error.

💡 Hint

Winston has a built-in way to catch uncaught exceptions.

Winston can handle uncaught exceptions by configuring an exceptions handler with transports like File.