Serving from multiple directories in Express - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to serve static files from the 'public' directory using Express.

Express

app.use(express.static('[1]'));

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

Afiles

Bassets

Cstatic

Dpublic

Attempts:

3 left

💡 Hint

Common Mistakes

Using a directory name that does not exist.

Forgetting to use express.static middleware.

The express.static middleware serves files from the specified directory. Here, 'public' is the folder containing static files.

2fill in blank

medium

Complete the code to serve static files from the 'images' directory under the '/img' URL path.

Express

app.use('/img', express.static('[1]'));

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

Apublic/images

Bimg

Cimages

Dstatic/images

Attempts:

3 left

💡 Hint

Common Mistakes

Including the URL path in the folder name.

Using a wrong folder path.

The express.static middleware serves files from the 'images' folder. The URL path '/img' maps to this folder.

3fill in blank

hard

Fix the error in the code to serve static files from both 'public' and 'assets' directories.

Express

app.use(express.static('[1]'));
app.use(express.static('assets'));

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

Apublic

Bassets

Cstatic

Dfiles

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same directory twice.

Trying to serve multiple directories in one call.

To serve multiple directories, call express.static for each folder. The first call should use 'public'.

4fill in blank

hard

Fill both blanks to serve static files from 'public' at root and 'uploads' at '/files'.

Express

app.use(express.static('[1]'));
app.use('/files', express.static('[2]'));

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

Apublic

Buploads

Cassets

Dstatic

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing folder names and URL paths.

Using wrong folder names.

The first middleware serves 'public' at root. The second serves 'uploads' under '/files' URL path.

5fill in blank

hard

Fill all three blanks to serve 'public' at root, 'images' at '/img', and 'downloads' at '/dl'.

Express

app.use(express.static('[1]'));
app.use('/img', express.static('[2]'));
app.use('/dl', express.static('[3]'));

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

Apublic

Bimages

Cdownloads

Dassets

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping folder names.

Using incorrect URL paths.

Each express.static call serves a folder at the specified URL path.

Practice

1. What happens when you use multiple app.use(express.static()) calls with different directories in Express?

easy

A. Express throws an error if multiple static directories are used.

B. Express merges all directories into one and serves files randomly from any directory.

C. Express only serves files from the last directory added with express.static().

D. Express serves static files by checking each directory in the order they were added until it finds the file.

Solution

1. Step 1: Understand how Express static middleware works

   Each app.use(express.static()) adds a middleware that checks its directory for requested files.

2. Step 2: Order of middleware matters

   Express checks these middlewares in the order they were added and serves the first matching file it finds.

3. Final Answer:

   Express serves static files by checking each directory in the order they were added until it finds the file. -> Option D

4. Quick Check:

   Multiple static folders checked in order = D [OK]

Hint: Remember: Express checks static folders in order added [OK]

Common Mistakes:

• Thinking Express merges directories randomly
• Believing only the last directory is used
• Assuming multiple static folders cause errors

2. Which of the following is the correct way to serve static files from two directories named public and assets in Express?

easy

A. app.use(express.static('public')); app.use(express.static('assets'));

B. app.use(express.static(['public', 'assets']));

C. app.use(express.static('public', 'assets'));

D. app.use(express.static('public')); app.use.static('assets');

Solution

1. Step 1: Check Express static syntax

   The express.static() middleware accepts only one directory path at a time.

2. Step 2: Use multiple app.use() calls

   To serve multiple directories, call app.use(express.static()) separately for each directory.

3. Final Answer:

   app.use(express.static('public')); app.use(express.static('assets')); -> Option A

4. Quick Check:

   Multiple static folders need separate app.use calls = C [OK]

Hint: Use separate app.use calls for each static folder [OK]

Common Mistakes:

• Passing multiple directories in one express.static call
• Using incorrect method like app.use.static
• Passing an array instead of separate calls

3. Given the code below, what file will Express serve when a user requests /image.png? Assume both directories contain a file named image.png.

app.use(express.static('public'));
app.use(express.static('assets'));

medium

A. The image.png from the public directory.

B. The image.png from the assets directory.

C. An error because the file exists in both directories.

D. No file will be served; Express will return 404.

Solution

1. Step 1: Understand middleware order

   Express checks static directories in the order they are added. Here, public is checked first.

2. Step 2: First match is served

   Since image.png exists in public, Express serves that file and stops checking further.

3. Final Answer:

   The image.png from the public directory. -> Option A

4. Quick Check:

   First matching static file served = A [OK]

Hint: Express serves first found file in order of static folders [OK]

Common Mistakes:

• Assuming Express merges files from both directories
• Thinking Express throws error on duplicates
• Believing the last directory has priority

4. Identify the error in the following Express code that tries to serve static files from two directories:

app.use(express.static('public'));
app.use(express.static));
app.use(express.static('assets'));

medium

A. The first line should use app.get instead of app.use.

B. The second line has a syntax error with missing parentheses and argument.

C. Express cannot serve from more than one directory.

D. The third line should come before the first line.

Solution

1. Step 1: Check each line for syntax correctness

   The second line is app.use(express.static)); which is missing parentheses and directory argument.

2. Step 2: Understand correct usage of express.static

   The express.static() function requires a directory path as an argument and proper parentheses.

3. Final Answer:

   The second line has a syntax error with missing parentheses and argument. -> Option B

4. Quick Check:

   Syntax error in express.static call = B [OK]

Hint: Check parentheses and arguments in express.static calls [OK]

Common Mistakes:

• Ignoring missing parentheses or arguments
• Thinking app.use is wrong for static files
• Believing order of calls causes syntax error

5. You want to serve static files from public and uploads directories, but only files in uploads should be accessible under the URL path /files. How do you configure Express correctly?

hard

A. app.use(express.static('public/uploads'));
app.use(express.static('uploads'));

B. app.use('/files', express.static('public'));
app.use(express.static('uploads'));

C. app.use(express.static('public'));
app.use('/files', express.static('uploads'));

D. app.use(express.static('public'));
app.use(express.static('/files/uploads'));

Solution

1. Step 1: Serve public directory normally

   Use app.use(express.static('public')) to serve files at root URL.

2. Step 2: Mount uploads directory under /files path

   Use app.use('/files', express.static('uploads')) so files in uploads are accessible under /files URL prefix.

3. Final Answer:

   app.use(express.static('public')); app.use('/files', express.static('uploads')); -> Option C

4. Quick Check:

   Use URL prefix for uploads folder = A [OK]

Hint: Use URL path prefix in app.use for selective static serving [OK]

Common Mistakes:

• Serving uploads without URL prefix
• Using wrong directory paths
• Confusing URL path with filesystem path