Implement comment sorting and nesting
Company: Bobyard
Role: Software Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Technical Screen
You are given mock comment data on the frontend. Each comment has:
- `id`: unique comment ID
- `userId`: author ID
- `timestamp`: creation time
- `content`: comment text
- `parentId`: nullable parent comment ID
Implement the frontend behavior for a comment UI:
1. Display comments sorted by either `timestamp` or `userId`.
2. Support both ascending and descending order.
3. Preserve the user's selected sort field and sort direction after a page refresh.
4. Build nested comments from the flat input using `parentId` only; do not change the backend.
5. Add a text filter on `content` so that only comments matching the filter and all of their descendants are shown. Unrelated branches must be hidden.
You may assume the data is provided locally as mock data.
Overview: This question evaluates skills in frontend data handling and UI behavior, including implementing sortable lists, maintaining user-selected sort field and direction across refreshes, constructing nested comment trees from flat parentId references, and filtering content while preserving descendant visibility.
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