Uploading files in Firebase - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a reference to the storage location.

Firebase

const storageRef = firebase.storage().ref().[1]('images/photo.jpg');

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

Aupload

Bchild

Cget

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'upload' instead of 'child' to create a reference.

Trying to use 'get' or 'delete' before creating the reference.

The child method creates a reference to a specific file path in Firebase Storage.

2fill in blank

medium

Complete the code to upload a file to Firebase Storage.

Firebase

storageRef.[1](file).then(() => console.log('Upload complete'));

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

AgetDownloadURL

BlistAll

Cput

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'getDownloadURL' instead of 'put' to upload.

Trying to use 'delete' or 'listAll' which are unrelated to uploading.

The put method uploads the file to the storage reference.

3fill in blank

hard

Fix the error in the code to get the download URL after upload.

Firebase

storageRef.put(file).then(() => storageRef.[1]()).then(url => console.log(url));

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

Adelete

Bupload

Clist

DgetDownloadURL

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'upload' again instead of 'getDownloadURL'.

Trying to use 'delete' or 'list' which do not return URLs.

After uploading, use getDownloadURL() to get the file's URL.

4fill in blank

hard

Fill both blanks to delete a file and then log a success message.

Firebase

storageRef.[1]().then(() => console.log([2]));

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

Adelete

B'File deleted successfully'

C'Upload complete'

Dput

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'put' instead of 'delete' to remove files.

Logging the wrong message after deletion.

Use delete() to remove the file, then log a success message.

5fill in blank

hard

Fill all three blanks to upload a file, get its URL, and log it.

Firebase

storageRef.[1](file).then(() => storageRef.[2]()).then([3] => console.log([3]));

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

Aput

BgetDownloadURL

Curl

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up method names or variable names.

Using 'delete' instead of 'put' or 'getDownloadURL'.

First, put uploads the file. Then, getDownloadURL gets the URL. Finally, the URL is logged using the variable url.

Practice

1. What is the main purpose of uploading files to Firebase Storage?

easy

A. To save files in the cloud for easy access and backup

B. To delete files from the user's device

C. To convert files into text format

D. To run files as programs on Firebase servers

Solution

1. Step 1: Understand file upload purpose

   Uploading files to Firebase Storage means saving them remotely in the cloud.

2. Step 2: Identify the benefit

   Files saved in the cloud can be accessed anytime and are backed up safely.

3. Final Answer:

   To save files in the cloud for easy access and backup -> Option A

4. Quick Check:

   Uploading files = cloud storage [OK]

Hint: Uploading means saving files online for backup and access [OK]

Common Mistakes:

• Thinking upload deletes local files
• Confusing upload with file conversion
• Believing upload runs files on server

2. Which Firebase Storage method is used to create a reference to a file location before uploading?

easy

A. firebase.storage().ref()

B. firebase.storage().upload()

C. firebase.storage().download()

D. firebase.storage().delete()

Solution

1. Step 1: Identify method to create file location

   firebase.storage().ref() creates a reference to a storage path.

2. Step 2: Confirm usage before upload

   You must create a reference before uploading a file to specify where it goes.

3. Final Answer:

   firebase.storage().ref() -> Option A

4. Quick Check:

   Reference method = ref() [OK]

Hint: Use ref() to point where file will be stored [OK]

Common Mistakes:

• Using upload() directly without ref()
• Confusing download() with upload process
• Trying to delete before uploading

3. What will the following code print if the upload is successful?

const storageRef = firebase.storage().ref('images/photo.jpg');
storageRef.put(file).then(() => console.log('Upload complete')).catch(() => console.log('Upload failed'));

medium

A. Upload failed

B. No output

C. Upload complete

D. SyntaxError

Solution

1. Step 1: Analyze the upload promise

   storageRef.put(file) returns a promise that resolves on success.

2. Step 2: Check the then() handler

   On success, it logs 'Upload complete' to the console.

3. Final Answer:

   Upload complete -> Option C

4. Quick Check:

   Successful upload logs 'Upload complete' [OK]

Hint: Successful upload triggers then() logging 'Upload complete' [OK]

Common Mistakes:

• Assuming catch() runs on success
• Confusing promise syntax
• Expecting no output on success

4. Identify the error in this Firebase file upload code:

const ref = firebase.storage().ref('docs/report.pdf');
ref.put(file).then(() => console.log('Done'));
console.log('Upload started');

medium

A. console.log('Upload started') should be inside then()

B. ref.put() should be ref.upload()

C. ref() is not a valid method

D. Missing catch() to handle upload errors

Solution

1. Step 1: Check upload method correctness

   ref.put(file) is correct to upload files in Firebase Storage.

2. Step 2: Look for error handling

   There is no catch() to handle possible upload failures, which is a best practice.

3. Final Answer:

   Missing catch() to handle upload errors -> Option D

4. Quick Check:

   Always add catch() for upload errors [OK]

Hint: Always add catch() after then() to catch errors [OK]

Common Mistakes:

• Using ref.upload() instead of ref.put()
• Placing console.log before upload completion
• Thinking ref() is invalid method

5. You want to upload a user profile picture and ensure the file is stored under 'users/{userId}/profile.jpg'. Which code snippet correctly sets the storage reference and uploads the file for user ID 'abc123'?

hard

A. const ref = firebase.storage().ref('profile.jpg/users/abc123'); ref.put(file);

B. const ref = firebase.storage().ref('users/abc123/profile.jpg'); ref.put(file);

C. const ref = firebase.storage().ref('users/profile.jpg/abc123'); ref.put(file);

D. const ref = firebase.storage().ref('abc123/users/profile.jpg'); ref.put(file);

Solution

1. Step 1: Understand the required path format

   The file must be stored under 'users/{userId}/profile.jpg', so 'users/abc123/profile.jpg' is correct.

2. Step 2: Verify the code snippet

   const ref = firebase.storage().ref('users/abc123/profile.jpg'); ref.put(file); uses the correct path and calls ref.put(file) to upload.

3. Final Answer:

   const ref = firebase.storage().ref('users/abc123/profile.jpg'); ref.put(file); -> Option B

4. Quick Check:

   Correct path format = users/abc123/profile.jpg [OK]

Hint: Use 'users/{userId}/profile.jpg' path format for user files [OK]

Common Mistakes:

• Mixing folder order in path
• Placing userId after filename
• Using incorrect slashes or order