Why efficient reads matter in Firebase - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to read data efficiently from Firebase.

Firebase

const docRef = db.collection('users').doc([1]);

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

Ausers

Bdata()

C'userId123'

Dget()

Attempts:

3 left

💡 Hint

Common Mistakes

Using collection name instead of document ID

Calling get() inside doc()

We need to specify the exact document ID to read efficiently, so 'userId123' is correct.

2fill in blank

medium

Complete the code to fetch only the needed fields from a document.

Firebase

docRef.get().then(snapshot => { const data = snapshot.[1](); });

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

Adata

Bfetch

Cread

Dget

Attempts:

3 left

💡 Hint

Common Mistakes

Using get() instead of data() on snapshot

Trying to fetch fields directly without calling data()

The method to get document data from a snapshot is data().

3fill in blank

hard

Fix the error in the query to limit reads to 10 documents.

Firebase

db.collection('posts').[1](10).get();

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Afilter

Bwhere

CorderBy

Dlimit

Attempts:

3 left

💡 Hint

Common Mistakes

Using filter() which does not exist

Using where() without conditions

Using orderBy() without limit()

The correct method to limit the number of documents read is limit().

4fill in blank

hard

Fill both blanks to create a query that reads only active users and limits to 5 results.

Firebase

db.collection('users').[1]('status', '==', 'active').[2](5).get();

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

Awhere

Blimit

CorderBy

Dfilter

Attempts:

3 left

💡 Hint

Common Mistakes

Using filter() which is not a Firebase method

Swapping limit() and where() order

Use where() to filter active users and limit() to restrict to 5 reads.

5fill in blank

hard

Fill all three blanks to read documents ordered by timestamp, filtered by type, and limited to 3.

Firebase

db.collection('events').[1]('type', '==', 'click').[2]('timestamp').[3](3).get();

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

Awhere

BorderBy

Climit

Dfilter

Attempts:

3 left

💡 Hint

Common Mistakes

Using filter() instead of where()

Changing the order of method calls

Omitting limit() causing too many reads

Use where() to filter by type, orderBy() to sort by timestamp, and limit() to restrict reads.