Morgan for HTTP request logging in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import Morgan middleware in an Express app.

Express

const express = require('express');
const morgan = require('[1]');
const app = express();

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

Aexpress

Blogger

Chttp

Dmorgan

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'express' instead of 'morgan' in require.

Using a wrong package name like 'logger'.

You import Morgan by requiring the 'morgan' package. This lets you use Morgan for logging HTTP requests.

2fill in blank

medium

Complete the code to use Morgan middleware with the 'dev' format in the Express app.

Express

app.use([1]('dev'));

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

Aexpress

Blogger

Cmorgan

Dhttp

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'express' instead of 'morgan'.

Forgetting to call the function with parentheses.

Use morgan('dev') to add Morgan middleware with the 'dev' logging format.

3fill in blank

hard

Fix the error in the code to log HTTP requests to a file using Morgan.

Express

const fs = require('fs');
const path = require('path');
const accessLogStream = fs.createWriteStream(path.join(__dirname, '[1]'), { flags: 'a' });
app.use(morgan('combined', { stream: accessLogStream }));

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

Aaccess.log

Baccesslog

Clog_access.txt

Daccess_log

Attempts:

3 left

💡 Hint

Common Mistakes

Using file names without extensions.

Using invalid or missing file names.

The log file name should be a valid string like 'access.log' to store logs properly.

4fill in blank

hard

Fill both blanks to create a custom Morgan token and use it in the log format.

Express

morgan.token('user-agent', function (req) { return req.headers['[1]']; });
app.use(morgan(':method :url :status :res[content-length] - :response-time ms :[2]'));

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

Auser-agent

Bcontent-type

Dreferer

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'content-type' or 'referer' instead of 'user-agent'.

Mismatching token names in definition and format.

The header name is 'user-agent' and the token name used in the format must match it exactly.

5fill in blank

hard

Fill all three blanks to create a conditional Morgan logger that skips logging for requests with status code 304.

Express

app.use(morgan('combined', {
  skip: function (req, res) {
    return res.statusCode [1] [2];
  },
  stream: [3]
}));

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

A===

B304

CaccessLogStream

D!==

Attempts:

3 left

💡 Hint

Common Mistakes

Using !== instead of === in skip condition.

Using wrong status code number.

Not setting the stream correctly.

The skip function returns true when status code is exactly 304, so Morgan skips logging those requests. The stream is set to the log file stream.

Practice

1. What is the main purpose of using morgan in an Express app?

easy

A. To log HTTP requests for monitoring server activity

B. To handle database connections

C. To serve static files

D. To manage user sessions

Solution

1. Step 1: Understand Morgan's role

   Morgan is a middleware that logs details about HTTP requests to the console or a file.

2. Step 2: Compare options with Morgan's function

   Only logging HTTP requests matches Morgan's purpose; other options relate to different tasks.

3. Final Answer:

   To log HTTP requests for monitoring server activity -> Option A

4. Quick Check:

   Logging HTTP requests = A [OK]

Hint: Morgan logs requests, not database or sessions [OK]

Common Mistakes:

• Confusing Morgan with session or static file middleware
• Thinking Morgan manages database connections
• Assuming Morgan serves files

2. Which of the following is the correct way to add Morgan middleware with the 'tiny' format in an Express app?

easy

A. app.use(morgan.format('tiny'))

B. app.use(morgan('tiny'))

C. app.use('morgan', 'tiny')

D. app.use(morgan.tiny())

Solution

1. Step 1: Recall Morgan usage syntax

   Morgan is used as middleware by calling morgan('format') inside app.use().

2. Step 2: Check each option's syntax

   Only app.use(morgan('tiny')) matches the correct syntax; others are invalid method calls or parameters.

3. Final Answer:

   app.use(morgan('tiny')) -> Option B

4. Quick Check:

   Use morgan('format') inside app.use() = D [OK]

Hint: Use morgan('format') inside app.use() exactly [OK]

Common Mistakes:

• Calling morgan as a method like morgan.tiny()
• Passing strings directly to app.use() without morgan()
• Using non-existent morgan.format() method

3. Given this Express code snippet, what will Morgan log when a GET request is made to '/'?

const express = require('express');
const morgan = require('morgan');
const app = express();
app.use(morgan('dev'));
app.get('/', (req, res) => res.send('Hello'));
app.listen(3000);

medium

A. GET / 200 5 - 0.123 ms

B. GET / 404 - - ms

C. POST / 200 5 - 0.123 ms

D. Error: Morgan format not found

Solution

1. Step 1: Identify the HTTP method and route

   The code handles GET requests to '/', so a GET / request is valid and returns 200 status.

2. Step 2: Understand Morgan 'dev' format output

   The 'dev' format logs method, URL, status code, response time, and response size roughly like 'GET / 200 5 - 0.123 ms'.

3. Final Answer:

   GET / 200 5 - 0.123 ms -> Option A

4. Quick Check:

   GET / with 200 status logs as in B [OK]

Hint: GET '/' with 'dev' logs method, URL, status, time [OK]

Common Mistakes:

• Confusing POST with GET method
• Assuming 404 status for existing route
• Expecting error from Morgan format

4. You added Morgan to your Express app with app.use(morgan('combined')), but no logs appear in the console. What is the most likely cause?

medium

A. Morgan requires a database connection to log

B. Morgan does not support 'combined' format

C. Morgan middleware is added after route handlers

D. Morgan only logs errors, not requests

Solution

1. Step 1: Understand middleware order importance

   Express runs middleware in order. If Morgan is added after routes, requests may not pass through it.

2. Step 2: Check Morgan format and behavior

   'combined' is a valid format; Morgan logs all requests, not just errors; it does not need a database.

3. Final Answer:

   Morgan middleware is added after route handlers -> Option C

4. Quick Check:

   Middleware order matters; Morgan must be before routes [OK]

Hint: Add Morgan before routes to see logs [OK]

Common Mistakes:

• Thinking 'combined' format is invalid
• Believing Morgan logs only errors
• Assuming Morgan needs a database

5. You want to log HTTP requests only if the response status is 400 or higher using Morgan. Which code snippet correctly achieves this?

hard

A. app.use(morgan('combined', { filter: (req, res) => res.statusCode >= 400 }))

B. app.use(morgan('combined', { skip: (req, res) => res.statusCode >= 400 }))

C. app.use(morgan('combined', { only: (req, res) => res.statusCode >= 400 }))

D. app.use(morgan('combined', { skip: (req, res) => res.statusCode < 400 }))

Solution

1. Step 1: Understand Morgan's skip option

   The 'skip' option is a function that returns true to skip logging that request.

2. Step 2: Apply condition to skip requests with status below 400

   To log only 400 or higher, skip requests where statusCode is less than 400.

3. Step 3: Verify other options

   'filter' and 'only' are not valid Morgan options; app.use(morgan('combined', { skip: (req, res) => res.statusCode >= 400 })) skips 400+ which is opposite of desired.

4. Final Answer:

   app.use(morgan('combined', { skip: (req, res) => res.statusCode < 400 })) -> Option D

5. Quick Check:

   Skip if status < 400 to log 400+ [OK]

Hint: Use skip to ignore status below 400 [OK]

Common Mistakes:

• Using skip condition backwards
• Using invalid options like filter or only
• Confusing skip with logging condition