Data aggregation patterns in Firebase - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to get a reference to the Firestore collection named 'orders'.

Firebase

const ordersRef = firestore.[1]('orders');

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

Acollection

Bdoc

Cget

Dset

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'doc' instead of 'collection' to get a collection reference.

Using 'get' or 'set' which are for reading or writing data, not referencing.

Use collection to get a reference to a Firestore collection.

2fill in blank

medium

Complete the code to increment the 'totalSales' field atomically in a Firestore document.

Firebase

docRef.update({ totalSales: firebase.firestore.FieldValue.[1](1) });

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Aincrement

Bdelete

CarrayUnion

DserverTimestamp

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'delete' which removes a field.

Using 'serverTimestamp' which sets the time, not increments.

The increment method atomically increases a numeric field.

3fill in blank

hard

Fix the error in the code to correctly aggregate the sum of 'amount' fields from multiple documents.

Firebase

let total = 0;
docs.forEach(doc => {
  total [1] doc.data().amount;
});

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A=

B*=

C-=

D+=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '=' which resets total instead of adding.

Using '-=' or '*=' which change the value incorrectly.

Use += to add each amount to the total sum.

4fill in blank

hard

Fill both blanks to create a Firestore query that gets documents where 'status' is 'completed' and orders by 'date' descending.

Firebase

const query = collectionRef.where('status', '==', [1]).[2]('date', 'desc');

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A'completed'

B'pending'

CorderBy

Dlimit

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'pending' instead of 'completed' for the filter.

Using 'limit' instead of 'orderBy' for sorting.

Use 'completed' to filter status and orderBy to sort by date descending.

5fill in blank

hard

Fill all three blanks to create a map of user IDs to their total order amounts, filtering orders above 100.

Firebase

const userTotals = {};
orders.forEach(order => {
  if (order.amount [1] 100) {
    const userId = order.[2];
    userTotals[userId] = (userTotals[userId] || 0) [3] order.amount;
  }
});

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

A>

BuserId

C+=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' for filtering.

Accessing wrong property instead of 'userId'.

Using '=' instead of '+=' for accumulation.

Use > to filter amounts above 100, access userId property, and += to accumulate totals.