Supported data types in Firebase - Commands & Configuration

Introduction

Firebase stores data in a flexible way using different types. Knowing these types helps you save and read data correctly without errors.

When you want to save a user's name as text in your app database

When you need to store a number like age or score for a player

When you want to save a list of items like shopping list or tasks

When you need to store true or false values for settings

When you want to save a date and time for events or logs

Commands

This command creates a Firestore document for user1 with different data types: string, number, boolean, array, and timestamp.

Terminal

firebase firestore:documents:create users/user1 --data '{"name":"Alice","age":30,"isActive":true,"tags":["admin","user"],"lastLogin":{"seconds":1625097600,"nanoseconds":0}}'

Expected Output

Document users/user1 created successfully.

→

--data - Specifies the data to store in the document using JSON format

This command retrieves the document for user1 to verify the stored data types and values.

Terminal

firebase firestore:documents:get users/user1

Expected Output

Document data for users/user1:

{

  "name": "Alice",

  "age": 30,

  "isActive": true,

  "tags": ["admin", "user"],

  "lastLogin": {

    "seconds": 1625097600,

    "nanoseconds": 0

  }

}

Key Concept

If you remember nothing else from this pattern, remember: Firebase supports strings, numbers, booleans, arrays, maps, and timestamps as main data types to store your app data.

Common Mistakes

Trying to store a date as a plain string instead of a timestamp object

This causes problems when querying or sorting by date because Firebase treats it as text, not time.

Use Firebase timestamp objects with seconds and nanoseconds fields to store dates.

Saving complex objects without using maps, just as strings

You lose the ability to query or update nested fields properly.

Use maps (nested JSON objects) to store structured data.

Summary

Use strings for text like names and descriptions.

Use numbers for counts, ages, or scores.

Use booleans for true/false settings.

Use arrays to store lists of values.

Use timestamps to store dates and times correctly.

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