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IndexedDB u0026 Web Storage Essentials for Mobile Hybrid Apps Quiz

This quiz explores key concepts of using IndexedDB and Web Storage in mobile hybrid app development, covering differences, use cases, and best practices for efficient client-side data management. Enhance your understanding of browser-based storage mechanisms for robust offline and persistent app experiences.

  1. Persistent Storage Options

    Which browser storage solution allows for storing large amounts of structured data, such as objects and arrays, making it suitable for complex offline features in a mobile hybrid app?

    1. SessionStorage
    2. IndexedDB
    3. Cookie
    4. WindowCache

    Explanation: IndexedDB enables developers to store significant amounts of structured data and supports objects, arrays, and even complex key-value pairs, making it ideal for advanced offline functionality. SessionStorage can only store strings and is cleared on browser close. WindowCache is not a standard storage solution for structured data. Cookies are limited in size and store only simple key-value string pairs, making them unsuitable for complex or large datasets.

  2. Web Storage Data Scope

    If you want data to be available only while a single tab is open in your mobile hybrid app, which storage method should you use?

    1. SessionStorage
    2. IndexedDB
    3. LocalStorage
    4. CacheStorage

    Explanation: SessionStorage keeps data accessible only within the current tab or window and is deleted when the tab is closed. IndexedDB and LocalStorage persist data across sessions and tabs. CacheStorage is intended for storing network resources, not for tab-limited data storage.

  3. Maximum Storage Limits

    Which storage type typically offers the largest storage quota for browser-based mobile hybrid apps?

    1. SessionStorage
    2. Cookies
    3. IndexedDB
    4. LocalStorage

    Explanation: IndexedDB provides much higher storage space compared to LocalStorage, SessionStorage, or Cookies, making it the preferred option for applications requiring large client-side data storage. LocalStorage and SessionStorage usually have limitations of 5-10 MB, and cookies have even smaller capacity. This makes Cookies and SessionStorage less suitable for storing large datasets.

  4. IndexedDB Transaction Example

    In IndexedDB, what is the proper sequence when saving an object after opening a database in a mobile hybrid app?

    1. Access object store, open database, create transaction, add object
    2. Open database, create transaction, access object store, add object
    3. Open database, access object store, add object, create transaction
    4. Add object, open database, create transaction, access object store

    Explanation: You must open the database first, then create a transaction, access the necessary object store through the transaction, and finally add the object. The other options present incorrect or illogical sequences that would cause errors, such as accessing stores before creating a transaction or adding objects before the database is open.

  5. Data Type Support in Web Storage

    Which data types can LocalStorage and SessionStorage directly store without conversion in mobile hybrid applications?

    1. Booleans and numbers
    2. Dates
    3. Strings only
    4. Objects and arrays

    Explanation: LocalStorage and SessionStorage can only store data as string values, so other data types must be converted to and from strings (for example, using JSON). Objects, arrays, booleans, and dates require manual stringification and parsing. This makes option B, C, and D incorrect for direct storage.

  6. Web Storage Key Persistence

    Which statement correctly describes the persistence behavior of LocalStorage in mobile hybrid apps?

    1. Data expires after a set time by default
    2. Data is cleared on tab close
    3. Data stays after app close and device restart
    4. Data is removed when the user logs out

    Explanation: LocalStorage persists data even after the browser or app is closed and the device is restarted, unless manually cleared. Closing a tab does not remove the data. Data is not automatically tied to user actions like logout unless coded that way. Unlike cookies, LocalStorage data does not have a default expiration.

  7. Atomic Operations in Storage APIs

    In the context of IndexedDB, what does it mean when an operation is described as 'atomic'?

    1. The operation completely succeeds or fails as a whole
    2. The operation is always synchronous
    3. The operation is split into multiple steps
    4. The operation can be partially complete

    Explanation: An atomic operation ensures that changes either all occur or none do, preventing partial writes and data corruption. IndexedDB transactions illustrate this well. The other options misunderstand atomicity: synchronous execution is unrelated, while splitting or partial completion would not be atomic.

  8. Use Case Scenarios

    For which scenario is IndexedDB a better choice than LocalStorage in a mobile hybrid app?

    1. Saving large lists of user data
    2. Storing one user preference
    3. Remembering a single login flag
    4. Simple number counters

    Explanation: IndexedDB is suitable for storing big or complex datasets like large lists of user data due to its structure and size limits. LocalStorage is ideal for small bits of data such as user preferences, login flags, or counters. The last three options don't require the advanced features provided by IndexedDB.

  9. Web Storage API Methods

    Which method should be used to remove a single item from LocalStorage in a mobile hybrid app?

    1. deleteStorage
    2. removeData
    3. clearAll
    4. removeItem

    Explanation: The removeItem method deletes a specific key and its value from LocalStorage. The clearAll and deleteStorage methods do not exist in the Web Storage API, and removeData is not a valid method for LocalStorage, which makes them incorrect choices.

  10. Security and Storage

    Why should sensitive information, like passwords, not be stored in LocalStorage or IndexedDB in a mobile hybrid app?

    1. They automatically encrypt stored data
    2. They have unlimited storage space
    3. These storage systems can be accessed by client-side scripts
    4. They force data to expire soon

    Explanation: LocalStorage and IndexedDB are accessible via client-side scripts, which means any malicious script running in the same context could potentially read sensitive information. These storage solutions do not automatically encrypt their data. Having lots of storage or forced expiry is not directly related to why storing sensitive data is unsafe in these places.

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