AsyncStorage for key-value in React Native - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import AsyncStorage from the correct package.

React Native

import [1] from '@react-native-async-storage/async-storage';

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

AAsyncStorage

BStorage

CAsyncStore

DStorageAsync

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong import names like StorageAsync or AsyncStore.

You must import AsyncStorage exactly from '@react-native-async-storage/async-storage' to use it.

2fill in blank

medium

Complete the code to save a value with AsyncStorage.

React Native

await AsyncStorage.[1]('username', 'john_doe');

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

AsetItem

BgetItem

CremoveItem

Dclear

Attempts:

3 left

💡 Hint

Common Mistakes

Using getItem instead of setItem to save data.

Use setItem to save a key-value pair in AsyncStorage.

3fill in blank

hard

Fix the error in the code to retrieve a value from AsyncStorage.

React Native

const value = await AsyncStorage.[1]('username');

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

AsetItem

BremoveItem

CgetItem

DsaveItem

Attempts:

3 left

💡 Hint

Common Mistakes

Using setItem or removeItem instead of getItem to read data.

Use getItem to retrieve a value by key from AsyncStorage.

4fill in blank

hard

Fill both blanks to remove a stored value and then clear all storage.

React Native

await AsyncStorage.[1]('username');
await AsyncStorage.[2]();

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

AremoveItem

Bclear

CgetItem

DsetItem

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing clear with removeItem or using getItem to delete.

removeItem deletes a specific key, and clear removes all keys from AsyncStorage.

5fill in blank

hard

Fill all three blanks to save, retrieve, and log a value using AsyncStorage.

React Native

await AsyncStorage.[1]('token', 'abc123');
const token = await AsyncStorage.[2]('token');
console.log([3]);

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

AsetItem

BgetItem

Ctoken

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Logging the wrong variable or mixing up setItem and getItem.

First, setItem saves the token. Then, getItem retrieves it. Finally, logging the variable token shows the stored value.

Practice

1. What is the main purpose of AsyncStorage in React Native?

easy

A. To create complex animations in the app

B. To handle network requests and API calls

C. To store small amounts of data as key-value pairs on the device

D. To manage app navigation between screens

Solution

1. Step 1: Understand AsyncStorage's role

   AsyncStorage is designed to save simple data like user preferences as key-value pairs on the device.

2. Step 2: Compare with other options

   Animations, network requests, and navigation are handled by other libraries or APIs, not AsyncStorage.

3. Final Answer:

   To store small amounts of data as key-value pairs on the device -> Option C

4. Quick Check:

   AsyncStorage = key-value storage [OK]

Hint: AsyncStorage saves simple data locally as key-value pairs [OK]

Common Mistakes:

• Confusing AsyncStorage with network or UI libraries
• Thinking AsyncStorage manages navigation or animations

2. Which of the following is the correct way to save a value using AsyncStorage in React Native?

easy

A. await AsyncStorage.setItem('key', 'value');

B. AsyncStorage.save('key', 'value');

C. AsyncStorage.store('key', 'value');

D. await AsyncStorage.put('key', 'value');

Solution

1. Step 1: Recall AsyncStorage method for saving data

   The correct method to save data is setItem, which returns a promise and requires await.

2. Step 2: Check method names

   Methods like save, store, and put do not exist in AsyncStorage API.

3. Final Answer:

   await AsyncStorage.setItem('key', 'value'); -> Option A

4. Quick Check:

   Save data = setItem [OK]

Hint: Use setItem with await to save data [OK]

Common Mistakes:

• Using incorrect method names like save or put
• Forgetting to use await with async calls

3. What will be logged to the console after running this code?

import AsyncStorage from '@react-native-async-storage/async-storage';

async function test() {
  await AsyncStorage.setItem('name', 'Alice');
  const value = await AsyncStorage.getItem('name');
  console.log(value);
}
test();

medium

A. Alice

B. null

C. Error: AsyncStorage not found

D. undefined

Solution

1. Step 1: Analyze setItem and getItem usage

   The code saves the string 'Alice' under the key 'name' and then retrieves it correctly using await.

2. Step 2: Understand console output

   Since the value was saved and retrieved successfully, console.log prints 'Alice'.

3. Final Answer:

   Alice -> Option A

4. Quick Check:

   Saved value retrieved = Alice [OK]

Hint: getItem returns saved string or null if missing [OK]

Common Mistakes:

• Expecting undefined instead of null or string
• Not awaiting async calls causing errors

4. Identify the error in this AsyncStorage usage:

import AsyncStorage from '@react-native-async-storage/async-storage';

function saveData() {
  AsyncStorage.setItem('token', 'abc123');
  console.log('Token saved');
}
saveData();

medium

A. console.log should be inside a .then() callback

B. Wrong method name setItem should be saveItem

C. AsyncStorage must be imported from 'react-native' not '@react-native-async-storage/async-storage'

D. Missing await before AsyncStorage.setItem causing unhandled promise

Solution

1. Step 1: Check async usage of setItem

   AsyncStorage.setItem returns a promise and should be awaited or handled with then to ensure completion.

2. Step 2: Identify missing await

   The function saveData is not async and does not await setItem, so the promise is unhandled and may cause issues.

3. Final Answer:

   Missing await before AsyncStorage.setItem causing unhandled promise -> Option D

4. Quick Check:

   AsyncStorage.setItem needs await [OK]

Hint: Always await AsyncStorage async calls to avoid unhandled promises [OK]

Common Mistakes:

• Forgetting to make function async and use await
• Using wrong import source
• Incorrect method names

5. You want to remove a saved user preference with key 'theme' and then confirm it is removed. Which code snippet correctly does this?

hard

A. await AsyncStorage.clear('theme'); const val = await AsyncStorage.getItem('theme'); console.log(val);

B. await AsyncStorage.removeItem('theme'); const val = await AsyncStorage.getItem('theme'); console.log(val);

C. AsyncStorage.delete('theme'); const val = AsyncStorage.get('theme'); console.log(val);

D. AsyncStorage.remove('theme'); const val = AsyncStorage.getItem('theme'); console.log(val);

Solution

1. Step 1: Identify correct method to remove a key

   The correct method to remove a key is removeItem, which returns a promise and should be awaited.

2. Step 2: Confirm removal by getting the key

   After removal, calling getItem returns null, confirming deletion.

3. Final Answer:

   await AsyncStorage.removeItem('theme'); const val = await AsyncStorage.getItem('theme'); console.log(val); -> Option B

4. Quick Check:

   Remove key = removeItem + await [OK]

Hint: Use removeItem with await to delete keys safely [OK]

Common Mistakes:

• Using non-existent methods like delete or remove
• Not awaiting async calls
• Using clear which removes all keys, not one