Array-contains queries in Firebase - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the array-contains query operator do in Firebase?

It finds documents where a specified array field contains a specific value.

beginner

Can array-contains queries check for multiple values at once?

No, array-contains checks for only one value. To check multiple values, use array-contains-any.

beginner

What type of field must you use array-contains on?

The field must be an array type in the document.

intermediate

Is it possible to combine array-contains with other query filters?

Yes, you can combine array-contains with other filters like where clauses, but only one array-contains filter per query.

beginner

What happens if you use array-contains on a field that is not an array?

The query will not match any documents because the field must be an array to contain values.

What does the Firebase array-contains operator do?

A Finds documents where an array contains any of multiple values

B Finds documents where a string contains a substring

C Finds documents where an array field contains a specific value

D Finds documents where a number is greater than a value

array-contains checks if a specific value exists inside an array field in documents.

Which operator allows checking if an array contains any of multiple values?

A array-contains-any

B array-contains

C in

D where

array-contains-any checks if the array contains at least one value from a list.

How many array-contains filters can you use in a single Firebase query?

A Unlimited

B One

C Two

D None

Firebase allows only one array-contains filter per query.

What type of field must be queried with array-contains?

A String

B Boolean

C Number

D Array

The field must be an array to use array-contains.

If a field is not an array, what will happen when using array-contains?

A It matches no documents

B It throws an error

C It matches documents with null values

D It matches documents anyway

The query will not match any documents if the field is not an array.

Explain how the array-contains query works in Firebase and when you would use it.

Think about searching for a value inside a list stored in a document.

Describe the difference between array-contains and array-contains-any in Firebase queries.

One is for single value, the other for multiple values.