Data validation rules in Firebase - Mini Project: Build & Apply

Firebase Data Validation Rules

📖 Scenario: You are building a simple Firebase Realtime Database to store user profiles. Each user has a unique ID, a name, and an age. You want to make sure that the data entered is correct and safe by using Firebase data validation rules.

🎯 Goal: Create Firebase Realtime Database validation rules that allow only user profiles with a name as a non-empty string and an age as a number between 1 and 120. Also, ensure that the user ID is a valid key.

📋 What You'll Learn

Create a users node in the database

Add a validation rule to check that name is a string and not empty

Add a validation rule to check that age is a number between 1 and 120

Ensure the user ID key is a valid Firebase key

💡 Why This Matters

🌍 Real World

Firebase data validation rules protect your database from bad or malicious data by enforcing correct data formats and values.

💼 Career

Understanding Firebase rules is essential for backend and full-stack developers working with Firebase to ensure data integrity and security.

1

Create the users node structure

Create a Firebase Realtime Database rules object with a users node that allows read and write access for now.

Firebase

{
  "rules": {
    "users": {
      // Your code here
    }
  }
}

Need a hint?

Start by allowing all reads and writes on the users node.

2

Add validation for name field

Inside the users node, add a $userId wildcard and create a name child validation rule that checks if newData.isString() and newData.val().length > 0.

Firebase

{
  "rules": {
    "users": {
      "$userId": {
        // Your code here
      },
      ".read": true,
      ".write": true
    }
  }
}

Need a hint?

Use $userId as a wildcard for user keys and validate the name field inside it.

3

Add validation for age field

Inside the $userId node, add an age child validation rule that checks if newData.isNumber() and newData.val() >= 1 and newData.val() <= 120.

Firebase

{
  "rules": {
    "users": {
      "$userId": {
        "name": {
          ".validate": "newData.isString() && newData.val().length > 0"
        },
        "age": {
          // Your code here
        },
        ".read": true,
        ".write": true
      }
    }
  }
}

Need a hint?

Validate that age is a number between 1 and 120 inclusive.

4

Validate the $userId key format

Add a validation rule on the $userId wildcard to ensure the key matches the regex ^[a-zA-Z0-9_-]+$ using newData.exists() and newData.key.matches().

Firebase

{
  "rules": {
    "users": {
      "$userId": {
        ".validate": "",
        "name": {
          ".validate": "newData.isString() && newData.val().length > 0"
        },
        "age": {
          ".validate": "newData.isNumber() && newData.val() >= 1 && newData.val() <= 120"
        },
        ".read": true,
        ".write": true
      }
    }
  }
}

Need a hint?

Use newData.key.matches() to check the user ID format.