path.extname for file extensions in Node.js - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the 'path' module in Node.js.

Node.js

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

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

Afs

Bhttp

Cpath

Durl

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'fs' instead of 'path' to import the module.

Forgetting to use quotes around the module name.

The path module is a built-in Node.js module used for handling file paths. You import it using require('path').

2fill in blank

medium

Complete the code to get the file extension from the filename.

Node.js

const ext = path.[1]('example.txt');

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

Abasename

Bextname

Cdirname

Djoin

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'basename' which returns the filename, not the extension.

Using 'dirname' which returns the directory path.

The extname method returns the extension of a file path, including the dot.

3fill in blank

hard

Fix the error in the code to correctly get the extension of 'archive.tar.gz'.

Node.js

const extension = path.[1]('archive.tar.gz');

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

Aextname

Bbasename

Cparse

Dformat

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'basename' which returns the full filename.

Using 'parse' or 'format' which are for different purposes.

The extname method returns the extension including the last dot and characters after it. For 'archive.tar.gz', it returns '.gz'.

4fill in blank

hard

Fill both blanks to get the extension of a file path stored in variable 'filePath'.

Node.js

const ext = path.[1]([2]);

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

Aextname

BfilePath

Cbasename

Ddirname

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'basename' instead of 'extname' for the method.

Using a string literal instead of the variable name.

Use path.extname(filePath) to get the extension of the file path stored in filePath.

5fill in blank

hard

Fill all three blanks to extract the extension and check if it equals '.js'.

Node.js

const ext = path.[1](filename);
if (ext === [2]) {
  console.log('This is a JavaScript file.');
}

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

Aextname

B'.js'

C'.txt'

Dbasename

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'basename' instead of 'extname'.

Comparing to '.txt' instead of '.js'.

Use path.extname(filename) to get the extension, then compare it to the string '.js' to check if the file is a JavaScript file.

Practice

1. What does path.extname('example.txt') return in Node.js?

easy

A. '.txt'

B. 'txt'

C. 'example.txt'

D. '' (empty string)

Solution

1. Step 1: Understand what path.extname does

   The path.extname method extracts the file extension including the dot from a filename string.

2. Step 2: Apply to 'example.txt'

   Since the file name is 'example.txt', the extension is '.txt' including the dot.

3. Final Answer:

   '.txt' -> Option A

4. Quick Check:

   Extension includes dot = '.txt' [OK]

Hint: Remember extname returns extension with dot [OK]

Common Mistakes:

• Forgetting the dot in the extension
• Returning the whole filename
• Returning empty string for files with extension

2. Which of the following is the correct syntax to get the extension of a file named 'photo.jpeg' using Node.js path module?

easy

A. path.extname('photo.jpeg')

B. path.extension('photo.jpeg')

C. path.getExt('photo.jpeg')

D. path.ext('photo.jpeg')

Solution

1. Step 1: Recall the correct method name

   The Node.js path module provides the method extname to get file extensions.

2. Step 2: Check the syntax

   The correct syntax is path.extname('filename'). Other options are invalid method names.

3. Final Answer:

   path.extname('photo.jpeg') -> Option A

4. Quick Check:

   Correct method is extname() [OK]

Hint: Use path.extname() exactly as named [OK]

Common Mistakes:

• Using incorrect method names like extension or ext
• Missing parentheses after method name
• Confusing with other path methods

3. What will be the output of the following code?

const path = require('path');
console.log(path.extname('archive.tar.gz'));

medium

A. '.tar.gz'

B. '' (empty string)

C. 'tar.gz'

D. '.gz'

Solution

1. Step 1: Understand how extname handles multiple dots

   The path.extname method returns the substring from the last dot to the end of the string.

2. Step 2: Apply to 'archive.tar.gz'

   The last dot is before 'gz', so the extension returned is '.gz'.

3. Final Answer:

   '.gz' -> Option D

4. Quick Check:

   Extension is from last dot = '.gz' [OK]

Hint: extname returns from last dot to end [OK]

Common Mistakes:

• Assuming it returns multiple extensions
• Returning empty string for multiple dots
• Including the whole suffix after first dot

4. Identify the error in this code snippet:

const path = require('path');
const ext = path.extname('document');
console.log(ext);

medium

A. It returns 'document' as extension

B. It throws an error because 'document' has no extension

C. It returns an empty string because no extension exists

D. It returns undefined

Solution

1. Step 1: Check the filename for extension

   The filename 'document' has no dot, so no extension exists.

2. Step 2: Understand extname behavior with no extension

   path.extname returns an empty string when no extension is found, not an error or undefined.

3. Final Answer:

   It returns an empty string because no extension exists -> Option C

4. Quick Check:

   No dot means empty string [OK]

Hint: No dot means extname returns empty string [OK]

Common Mistakes:

• Expecting an error for missing extension
• Expecting undefined instead of empty string
• Confusing filename with extension

5. You want to filter an array of filenames to only include '.js' files. Which code snippet correctly uses path.extname to do this?

const path = require('path');
const files = ['app.js', 'index.html', 'script.ts', 'readme'];
const jsFiles = files.filter(???);
console.log(jsFiles);

hard

A. file => path.extname(file) === ''

B. file => path.extname(file) === '.js'

C. file => path.extname(file) === '.JS'

D. file => path.extname(file) === 'js'

Solution

1. Step 1: Understand the filter condition

   We want to keep files whose extension is exactly '.js' including the dot and case-sensitive.

2. Step 2: Use path.extname correctly

   The correct comparison is path.extname(file) === '.js'. Other options either miss the dot, use wrong case, or check for empty extension.

3. Final Answer:

   file => path.extname(file) === '.js' -> Option B

4. Quick Check:

   Filter by exact '.js' extension [OK]

Hint: Compare extname result including dot and case [OK]

Common Mistakes:

• Omitting the dot in extension comparison
• Ignoring case sensitivity
• Filtering by empty string instead of '.js'