Meta Frontend Engineer System Design Questions

Managing notifications across different platforms and ensuring a user-friendly interface is paramount for keeping users engaged. This design focuses on a central notification management system.
Problem statement: Implement a class NotificationSystem that supports sending notifications and retrieving them by user.
- Method Signatures:
- constructor() — initializes the notification system.
- sendNotification(userId: string, message: string): void — sends a notification to the specified user.
- getNotifications(userId: string): string[] — retrieves notifications for the specified user.Example 1:
Input: system = new NotificationSystem(); system.sendNotification('user1', 'Welcome!');
Output: system.getNotifications('user1') => ['Welcome!']Constraints:
- 1 <= userId.length <= 10^5
- 1 <= message.length <= 500

Displaying images efficiently in a carousel format is essential for user engagement in photo-sharing apps. This design focuses on class structure that manages the image data, current state, and transition logic for the carousel.
Problem statement: Create a class ImageCarousel that manages images and transitions between them.
- Method Signatures:
- constructor(images: string[]) — initializes the carousel with the provided image URLs.
- next(): string — moves to the next image and returns the URL.
- prev(): string — moves to the previous image and returns the URL.
- getCurrentImage(): string — returns the URL of the current image.Example 1:
Input: carousel = new ImageCarousel(['img1.jpg', 'img2.jpg', 'img3.jpg'])
Output: carousel.getCurrentImage() => 'img1.jpg'
Output: carousel.next() => 'img2.jpg'Constraints:
- 1 <= images.length <= 100
- All strings in images are valid URLs.