Offline persistence in Firebase - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to enable offline persistence in Firebase Firestore.

Firebase

firebase.firestore().[1]();

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

AenablePersistence

BdisablePersistence

CstartPersistence

DsetPersistence

Attempts:

3 left

💡 Hint

Common Mistakes

Using disablePersistence instead of enablePersistence

Trying to call a non-existent method like startPersistence

Calling enablePersistence() activates offline data persistence in Firestore.

2fill in blank

medium

Complete the code to catch errors when enabling offline persistence.

Firebase

firebase.firestore().enablePersistence().catch(function([1]) {
  if ([1].code == 'failed-precondition') {
    console.log('Multiple tabs open, persistence failed.');
  }
});

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

Ae

Berr

Cerror

Dexception

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name not matching the catch parameter

Leaving the parameter blank

The error object is commonly named error in the catch function.

3fill in blank

hard

Fix the error in the code to enable offline persistence with multi-tab support.

Firebase

firebase.firestore().enablePersistence([1]: true});

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

AenableMultiTab

BsyncTabs

CmultiTab

DsynchronizeTabs

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect option names like syncTabs or multiTab

Missing the curly braces around the option

The correct option to enable multi-tab synchronization is synchronizeTabs.

4fill in blank

hard

Fill both blanks to handle the 'unimplemented' error when enabling persistence.

Firebase

firebase.firestore().enablePersistence().catch(function(error) {
  if (error.code === [1]) {
    console.log('Persistence is not available in this browser.');
  }
  else if (error.code === [2]) {
    console.log('Multiple tabs open, persistence failed.');
  }
});

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

A'unimplemented'

B'failed-precondition'

C'permission-denied'

D'network-error'

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up error codes

Using unrelated error codes like 'permission-denied'

The 'unimplemented' code means persistence is not supported. 'failed-precondition' means multiple tabs conflict.

5fill in blank

hard

Fill all three blanks to initialize Firestore with offline persistence and multi-tab synchronization.

Firebase

const db = firebase.firestore();
db.[1]([2]: true).catch(function(error) {
  if (error.code === [3]) {
    console.log('Persistence failed due to multiple tabs.');
  }
});

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

AenablePersistence

BsynchronizeTabs

C'failed-precondition'

DdisablePersistence

Attempts:

3 left

💡 Hint

Common Mistakes

Using disablePersistence instead of enablePersistence

Wrong option name for multi-tab sync

Incorrect error code in catch block

Use enablePersistence with synchronizeTabs: true to enable offline support across tabs. The error code 'failed-precondition' indicates multiple tabs conflict.