Array-contains queries in Firebase - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to query documents where the 'tags' array contains 'cloud'.

Firebase

const query = firestore.collection('articles').where('tags', '[1]', 'cloud');

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

Aarray-contains

B==

Cin

Darray-contains-any

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' instead of 'array-contains' for array fields.

Using 'in' which checks for values in a list, not inside arrays.

The 'array-contains' operator checks if an array field contains a specific value.

2fill in blank

medium

Complete the code to query documents where the 'categories' array contains any of the values in ['tech', 'science'].

Firebase

const query = firestore.collection('posts').where('categories', '[1]', ['tech', 'science']);

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

Aarray-contains-any

Bin

Carray-contains

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'array-contains' which only checks for one value.

Using 'in' which checks if a field equals any value in a list, not array contents.

The 'array-contains-any' operator checks if an array contains any of the specified values.

3fill in blank

hard

Fix the error in the query to find documents where 'skills' array contains 'firebase'.

Firebase

const query = firestore.collection('users').where('skills', '[1]', 'firebase');

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

A==

Barray-contains-any

Cin

Darray-contains

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' which does not work for array fields.

Using 'in' which is for matching field values, not array contents.

The correct operator to check if an array contains a specific value is 'array-contains'.

4fill in blank

hard

Fill both blanks to query documents where the 'features' array contains any of the values ['fast', 'reliable'], and limit to 5 results.

Firebase

const query = firestore.collection('products').where('features', '[1]', ['fast', 'reliable']).limit([2]);

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

Aarray-contains-any

Barray-contains

C5

D10

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'array-contains' which only accepts a single value, not an array.

Not setting a limit or using an invalid limit value.

Use 'array-contains-any' to check for multiple values in an array. Limit the results to 5 documents.

5fill in blank

hard

Fill all three blanks to query documents where 'tags' array contains 'cloud', order by 'date', and limit to 3 results.

Firebase

const query = firestore.collection('events').where('tags', '[1]', 'cloud').orderBy('[2]').limit([3]);

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

Aarray-contains

Bdate

C3

Dtimestamp

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'array-contains-any' when only one value is needed.

Ordering by a wrong field name.

Setting an invalid limit number.

Use 'array-contains' to filter by array value, order by 'date' field, and limit results to 3.