Supported data types in Firebase - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are the basic data types supported by Firebase Realtime Database?

Firebase Realtime Database supports strings, numbers, booleans, null, arrays, and objects as basic data types.

intermediate

How does Firebase store a timestamp value?

Firebase stores timestamps as numbers representing milliseconds since Unix epoch or using special server timestamp values.

intermediate

Can Firebase Realtime Database store binary data directly?

No, Firebase Realtime Database does not store binary data directly; binary data should be encoded as strings (e.g., base64) or stored in Firebase Storage.

advanced

What data type does Firebase Firestore support that Firebase Realtime Database does not?

Firestore supports additional data types like GeoPoint, Timestamp, and Reference types that are not available in Realtime Database.

intermediate

Why should you avoid using arrays in Firebase Realtime Database?

Arrays can cause issues with concurrent updates and indexing; it's better to use objects with unique keys for better scalability and data integrity.

Which of the following is NOT a supported data type in Firebase Realtime Database?

A String

B Function

C Boolean

D Number

Firebase Realtime Database does not support storing functions as data.

How should binary data be stored when using Firebase Realtime Database?

A As base64 encoded strings

B As JSON objects

C Directly as binary

D As numbers

Binary data should be encoded as base64 strings before storing in Firebase Realtime Database.

Which Firebase service supports GeoPoint data type?

A Realtime Database

B Cloud Storage

C Firestore

D Firebase Hosting

Firestore supports GeoPoint data type for storing geographic coordinates.

What is the recommended way to store lists in Firebase Realtime Database?

A Numbers

B Arrays

C Strings

D Objects with unique keys

Using objects with unique keys avoids issues with concurrent updates and indexing.

Which data type represents a null value in Firebase Realtime Database?

A null keyword

B Empty string

C Zero

D "null" string

Firebase uses the null keyword to represent null values.

List and describe the main data types supported by Firebase Realtime Database.

Think about simple data types and how collections are stored.

Explain why using objects with unique keys is preferred over arrays in Firebase Realtime Database.

Consider how multiple users might update data at the same time.

Practice

1. Which of the following is NOT a supported data type in Firebase Firestore?

easy

A. String

B. Function

C. Boolean

D. GeoPoint

Solution

1. Step 1: Review Firebase supported data types

   Firebase supports strings, booleans, numbers, arrays, maps, timestamps, and geopoints.

2. Step 2: Identify unsupported type

   Functions are not stored as data types in Firestore; they are part of code logic, not data.

3. Final Answer:

   Function -> Option B

4. Quick Check:

   Functions are not data types in Firestore [OK]

Hint: Remember: Firestore stores data, not code like functions [OK]

Common Mistakes:

• Confusing code functions with data types
• Thinking all JavaScript types are supported
• Assuming Firestore stores executable code

2. Which is the correct way to store a timestamp in Firebase Firestore?

easy

A. Store as a number representing milliseconds since epoch

B. Use a string with date format like '2024-06-01'

C. Use the Firebase Timestamp type

D. Use a boolean true or false

Solution

1. Step 1: Understand Firestore timestamp storage

   Firestore has a special Timestamp type to store date and time accurately.

2. Step 2: Compare options

   Strings and numbers can store dates but lack Firestore's timestamp features; booleans are unrelated.

3. Final Answer:

   Use the Firebase Timestamp type -> Option C

4. Quick Check:

   Timestamp type stores dates best [OK]

Hint: Use Firebase Timestamp for dates, not strings or numbers [OK]

Common Mistakes:

• Storing dates as plain strings
• Using numbers without Timestamp type
• Confusing booleans with dates

3. What will be the data type of the field location after this Firestore document is saved?

const docData = { location: new firebase.firestore.GeoPoint(40.7128, -74.0060) };

medium

A. GeoPoint

B. Array

C. String

D. Map

Solution

1. Step 1: Identify the data type used

   The code uses new firebase.firestore.GeoPoint() which creates a GeoPoint object.

2. Step 2: Understand Firestore storage

   Firestore stores GeoPoint objects as GeoPoint type, representing geographic coordinates.

3. Final Answer:

   GeoPoint -> Option A

4. Quick Check:

   GeoPoint stores latitude and longitude [OK]

Hint: GeoPoint objects store coordinates, not strings or arrays [OK]

Common Mistakes:

• Thinking GeoPoint is stored as string
• Assuming coordinates are arrays
• Confusing GeoPoint with map type

4. You try to save this data in Firestore:

{ name: 'Alice', age: '25' }

But you want age to be a number. What is the error and how to fix it?

medium

A. No error, Firestore converts string to number automatically

B. No error, but age should be stored as boolean true

C. Error: Firestore does not allow strings, use boolean instead

D. Error: age is string, fix by storing age as number 25

Solution

1. Step 1: Check data types in the object

   Age is stored as a string '25', not a number 25.

2. Step 2: Understand Firestore type strictness

   Firestore stores data as given; it does not convert string to number automatically.

3. Final Answer:

   Error: age is string, fix by storing age as number 25 -> Option D

4. Quick Check:

   Store numbers as numbers, not strings [OK]

Hint: Store numbers as numbers, not strings to avoid type errors [OK]

Common Mistakes:

• Assuming Firestore auto-converts types
• Using booleans for numbers
• Ignoring type mismatch warnings

5. You want to store a user's profile with name, age, location (latitude and longitude), and signup date in Firestore. Which data types should you use for location and signupDate fields?

hard

A. location as GeoPoint, signupDate as Timestamp

B. location as Map with lat/lng numbers, signupDate as string

C. location as Array of numbers, signupDate as number (milliseconds)

D. location as string 'lat,lng', signupDate as boolean true

Solution

1. Step 1: Identify best types for location and date

   Firestore provides GeoPoint for geographic coordinates and Timestamp for dates.

2. Step 2: Evaluate options

   Using GeoPoint and Timestamp ensures correct storage, querying, and indexing.

3. Final Answer:

   location as GeoPoint, signupDate as Timestamp -> Option A

4. Quick Check:

   Use GeoPoint and Timestamp for location and dates [OK]

Hint: Use GeoPoint for locations and Timestamp for dates [OK]

Common Mistakes:

• Storing dates as strings
• Using arrays for location
• Confusing booleans with dates