Limit and pagination in Firebase - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to limit the number of documents retrieved to 5.

Firebase

db.collection('users').limit([1]).get()

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

A15

B20

C5

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using a number larger than needed.

Forgetting to use the limit method.

The limit method restricts the number of documents returned. Here, setting it to 5 means only 5 documents will be fetched.

2fill in blank

medium

Complete the code to start the query after the last document snapshot stored in 'lastDoc'.

Firebase

db.collection('users').startAfter([1]).limit(5).get()

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

AfirstDoc

BlastDoc

CprevDoc

DnextDoc

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable that does not hold a document snapshot.

Confusing 'startAfter' with 'startAt'.

The startAfter method is used to continue fetching documents after a specific document snapshot. Here, 'lastDoc' is the last document from the previous query.

3fill in blank

hard

Fix the error in the code to correctly paginate documents by starting at the last document snapshot.

Firebase

db.collection('users').[1](lastDoc).limit(5).get()

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

AstartAfter

BstartAt

CendBefore

DendAt

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'startAt' which causes duplicate documents in pagination.

Using 'endAt' or 'endBefore' which are for ending queries.

startAfter is the correct method to start fetching documents after the given document snapshot, enabling pagination without repeating the last document.

4fill in blank

hard

Fill both blanks to create a query that orders users by 'age' and limits results to 10.

Firebase

db.collection('users').orderBy([1]).[2](10).get()

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

A'age'

Blimit

CstartAfter

D'name'

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'startAfter' instead of 'limit' for limiting results.

Ordering by a wrong field name.

The orderBy method sorts documents by the 'age' field. The limit method restricts the number of documents to 10.

5fill in blank

hard

Fill all three blanks to paginate users ordered by 'score', starting after 'lastDoc', limiting to 7 results.

Firebase

db.collection('users').orderBy([1]).[2]([3]).limit(7).get()

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

A'score'

BstartAfter

ClastDoc

Dlimit

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'limit' instead of 'startAfter' for pagination.

Not ordering by the correct field.

Passing a wrong variable to 'startAfter'.

This query orders users by 'score', starts after the last document snapshot 'lastDoc' to avoid duplicates, and limits the results to 7 documents.